Renewable Energy

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How much biogas from how much food waste? In general, that’s the question we left unanswered in that last blog, part 2 in this series. (Here… And part one is here, in case you missed it.)

Well, the rule of thumb is that a biogas digester kept at the proper temperature — body heat, which is 105 degrees Fahrenheit … or at least it is for a cow — will produce its own volume in biogas every day. According to this rule, if your digester is a cubic meter, and you keep it properly warm, you will get a cubic meter of biogas from it, every day. (That’s about 35 cubic feet, and comfortably more than most families will need to cook their lunch and dinner, but not a lot more.)

But that rule of thumb comes from experience with manure-fed digesters. That is, if you have a digester and you’re just putting manure in it, then the rule of thumb applies. But the fact is that different substrates produce different amounts of biogas. Remember when we said that food waste makes great biogas? (No? Well, we did….) You can see the difference by looking at the following chart which I produced, using data published by the Bavarian Association for the Promotion of Solar Energy:

substrates chart

Click on the graph to see a larger version. Source data derived from Solarenergiefoerderverein Bayern e. V., “Biogas– Strom und Wärme aus der Natur”, pg. 9 (here)

Freshly cut grass clippings can ultimately produce better than 1½ cubic feet of biogas per dried pound. By contrast, the same dry weight of cow manure, under the same conditions, will produce less than a quarter of that. If you’re lucky enough to have enough of what the Bavarians call “residual fats,” then the comparable pound will produce 24 times the amount of biogas as the cow manure. So like I said: different substrates produce different amounts of biogas. In spades.

Now, of course, all energy, but most especially small-scale (they call it) alternative energy, biogas included, is situational. It doesn’t matter how fancy/cool some to-be-purchased wind electric system is if you don’t have wind where you are. And you’ll never heat your water with the sun… at night. In the same way, it shouldn’t matter to you how great corn silage is for making biogas if you don’t have any corn silage. And as for “residual fats”— like used cooking oil, maybe?— the biodiesel folks probably have all that stuff snatched up before the fast food places have time to even think about pulling the last dripping French fry out of it.

But these days, almost any of us can get access to wasted food, stuff that gets tossed from places out all over town, restaurants, and cafeterias and grocery stores. Mark my words: A day will come when food waste will be as hard to get as used cooking oil is now. But for the time being, almost any of us can get just about as much as we want.

So again (since I still haven’t told you, right?) how much biogas can you get from your food waste digester?

Well, maybe I did give you the answer: about 4 (or more) times as much per dry pound as you could if you were using cow manure. In general, in other words, take the rule of thumb and multiply by 4.

And how much will you need? Well, what you really need to get detailed answers about your specific situation is more information. For example, to figure out how much biogas you need to heat your house, you need to know a lot about the weather outside, how large the house is, how well insulated, and things like that. That whole process is described in The Complete Biogas Handbook, chapter 28. The book will also tell you how to convert the burners on your stove to run on biogas, the practical details of designing your own digester, how to figure out things like how much hot water you need, how much biogas it will take to heat it, and all the cool stuff you need to know to really make practical use of biogas. Besides, when you visit the site you can find the best free information on the web about how to build any of the four most common home-scale digesters (on the “build” page).

Now, at this juncture, most explanations that I have seen about biogas get a bit coy, and they don’t give you really practical information in a clear form. We’re not going to do that. The chart below is like no other that I have seen in all my years of involvement with this subject.

The chart asumes two critical things: first, that you are digesting food waste, and second, that the digester is at body temp. Given just those two assumptions, it shows you how many 1-gallon buckets of food waste you need to be able to get the outcome you want— and what size of digester you’ll need too. Simple. Clear. Ready? Here it is:

Food waste power!
(Click here to see a larger version)
Use ft3
Notes ft3
Food waste
req’d, 1 gal
vol, gal
Lights, 100 w equiv. 2.5 2 lights, 3 hours in the evening 15 0.5 22
Cooking, per burner 20.0 2 burners, 2 hours, 2 meals 80 2.0 120
Hot water, per gal 4.5 Assume 30 gal/da for shower, dish washing, etc. 135 3.5 200
Engine, 100 HP 1600.0 Small engine (genset?), 4 hours/day 6400 160.0 9,600

(For hot water, we figured we would need to raise the temperature from
50° to 130°F, @40% efficiency, using biogas @60% methane.)

If you've been reading along with these blog posts, you'll know that in part 2, we mentioned that we were going to answer what is, for biogas, the ‘holy grail’ question: “Can I run my car on biogas?” Well, look at the chart. The answer seems pretty obvious: sure you can; but you need to get a hold of a couple of hundred one gallon buckets of food waste… every day. (That’s based on the thought that most cars have engines that are larger than 100 HP.)

What? Did you think I'd tell you some fairy tale? Cars are Big, Lumbering, Inefficient Energy Hogs. Does it really make sense that you could power one with three or four buckets of food waste?

If you do the math, you'll see that a standard engine requires about 16 ft3 per HP per hour. And that 100 HP engine? The digester needed to provide 4 daily hours of fuel for it (if kept at body temps) would be the size of an above-ground swimming pool: 20 feet across and 4 feet high. And keep looking. The chart can give you a lot more information like that ... And along those lines, notice that except for running your Range Rover, the biogas you need to provide light, cooking and hot water for an averagefamily can be produced if you can find 6 gallons of food waste a day. Is that a lot or a little?

So I think that's good, yeah? Biogas and food waste. And the folks who end up making food waste into biogas will be doing the rest of us a great big favor, because when that food waste gets put into the landfill, it produces methane there too. The difference is that the methane from the landfill goes into the atmosphere, and there…, well, it’s a very powerful greenhouse gas: it has 38 times the negative impact of carbon dioxide. But when we make biogas (and burn the biogas), all that methane is turned into carbon dioxide… and the impact of the food waste is dramatically reduced. Talk about a powerful way to reduce your carbon footprint: Think biogas.

Be a good guy. Make some food waste into biogas, and then burn the biogas, joyfully. (The first time you see that pale, almost invisble blue flame, you’ll be hooked, for sure.)

I think maybe in the next blog series we’ll say a few things about temperature, a really important parameter in biogas production. And, hey, just because I like you, I’m going to give you an Excel spreadsheet to calculate the effect of temperature on the digestion process. Keep reading...

David William House is the author of The Complete Biogas Handbook.


In mid-2012, we avid do-it-yourselfers cast a lustful eye on photovoltaic solar for our home. We reasoned that the sun was there every day – why not capture its free, clean and renewable energy? The thought enticed us not unlike Ralphie in A Christmas Story

Just like Ralphie, was enticed by the Red Rider BB gun, but held at bay by the threats of shooting his eye out, we were enticed by shiny solar possibilities with the threats of failing and being made a laughing stock (at best) or becoming a pile of incinerated ash (at worst). Danger does lurk around every corner for the novice and/or the careless, and extreme caution should be the rule. Being aware of this, we still decided the take the plunge and build the system ourselves. We began the build in January 2013. Six months later, we completed the project successfully and were up and running.

DIY Photovoltaic Solar Power 

Here is a picture of our finished system in front our home. We built an on-ground system for ease of maintenance and the ability to rotate the frames and capture more solar energy at different times of the year.

Advantages of DIY Home Solar Power

By taking on the project ourselves we were able to:
  • Capture more electricity by designing (manually-driven) automated rotated frames, which incorporate full tilt angle variation to track the sun all year.
  • Have on-grid/off-grid capability with the flip of a switch.
  • Capture free renewable energy and help keep the Earth clean.DIY Photovoltaic Solar Power

By designing and building the system ourselves, we estimate we saved over 70 percent. Our payback (with incentives included) is a mere 6.2 years. We realized that almost anyone, anywhere will benefit from photovoltaic solar energy. (See NASA charts at this link.)

We are delighted with our photovoltaic system and have written a book entitled DIY Photovoltaic Solar Power for Homeowners. In our book, we’ve included our detailed charts, wiring diagrams, parts lists, and energy analysis. We’re looking forward to sharing details of our system build and design in future blog posts.


One of the worst traits of humankind is our reliance on fossil fuels and the incessant depletion of non renewable resources. There are many alternatives and yet the majority of the world still acquires energy using practices which are causing irreversible damage to the earth, the people, the land, the air and the water. The exploitation of natural resources and reliance on coal powered plants and nuclear energy plants will lead to a dismal future if solution based renewable energy systems are not replaced as the norm.

Introducing Aur Beck

Luckily, individuals like Aur Beck are shedding light on the easy transition to choosing renewable energy. My dear friend, Aur 'da energy mon' Beck, has been immersed in the growing field of renewable energy since he was a teenager. In 1990 at age 15, after independently researching solar energy, Aur moved into a 12 volt,  battery operated camper in his parents’ driveway.

Aur translates as "light" or "to enlighten" in both Hebrew and Latin, a perfect name for a solar energy expert. According to Aur, “reading profusely and consistently tinkering with Renewable Energy (RE) has been a continuous constant throughout my life. Never officially attending school left me time to do in depth study, intern, view, and install renewable energy projects. Of course, working in one of the first United States passive solar schools helped.”

The Power of One

Aur is the president, chief tech, and coordinator of the Renewable Energy Install Network (Green Geek Squad) for Advanced Energy Solutions. Since 1999, he has been putting his knowledge to great use promoting, installing, & educating about renewable energy.

Aur has made significant contributions to Solar Energy in recent years. Aur sheds his light in many ways:

Founder and on the board for both the Illinois Renewable Energy Association and the Southern Illinois Center for a Sustainable Future
Started Oil Addicts Anonymous International
Hosts a weekly radio talk show called Your Community Spirit
AESsolar won the “Missouri Schools Going Solar” contract in 2005 and assisted with the sale and installation of 17 school systems
January 2007, trained presenter for Al Gore’s Climate Project
Based on the vast knowledge base Aur has in the field of renewable energy, he was invited to join the Midwest Solar Training Network (a DOE program) and to become an adjunct professor at Hocking Energy Institute in Logan, Ohio

Aur grew up on the family farm in the heart of the Shawnee National Forest, in an off-the-grid, solar-electric-powered home which makes it very easy to advocate for a life of simpler living, energy efficiency and renewable energy. Aur came up with and definitely lives by Advanced Energy Solutions slogan: We Empower YOU to Get Energized!

Dedication to Sustainable Living

I have been impressed with Aurs dedication to sustainable living and renewable energy since I first met him in 2000. One of Aurs most notable accomplishments in the last few years was being hand selected and invited to teach a semester of Solar PV Design and Installation by Neil Hinton, the Dean of the School of Engineering and Information Technology of the Hocking College Energy Institute in Nelsonville Ohio. This is impressive in light of the fact that Aur hasn’t been through any formal schooling whatsoever. He has no degree but he is a living breathing encyclopedia of all things solar. Aurs ability to confidently teach at a college level with no formal training is very inspiring. Not only does it encourage others to follow their dreams but it also offers a bit of insight into just how powerful it is to be passionate about what you do in life sans a degree.

At the Energy Institute, Aur inspired students by his minds on/ hands on teaching methods. He tested their knowledge initially to try and fill in the knowledge gaps throughout the semester. He gave them useful and practical knowledge which can actually be related to real world applications.

The reason he was selected to teach is due, in part, to him being double NABCEP certified. Helping students in the program taking The NABCEP, (North American Board of Certified Energy Practitioners) Entry Level knowledge test was his primary goal.

Inspiration is cyclical. Renewable energy can reshape the future.

Advanced Energy Solutions

To learn more about Aur and his company, please visit his website.  Advanced Energy Solutions offers:

Solar and Wind Generated Electricity
Energy Efficiency
Utility-Tied/Net Metered or Off-Grid Systems
System Design
System and Component Sales
On-site Consulting and Electric Load Analysis
Follow-up on Technical Assistance and Service
Training from Basic to Advanced hands installation
Training Programs-designing & installing hands on training labs

Aur also manages a living off-grid Facebook group.

Feeding an ARTI-style digester with a floating gas holder

Cliff hanger, right? We told you there was a gold mine in back of your local restaurant in part one of this subject series (here), and we waved somewhere toward the direction of using the “found energy” tied up in the carbon bonds of that wasted food for this and that. (We mentioned cooking with that energy, for example.)

So the question is: How? How can we make the energy which is potentially available in food waste into usable energy? Let’s see….

In the developing world, many things happen at the village or household scale. If we cook our own meals using wood that we’ve gone into the forest and gathered, that is a system that has a household scale. (And it would please Thoreau, eh? Wood fire warms you twice, he said.)

But virtually all our systems in the US are industrial scale (that is, Big), including our energy systems (consider those long electric lines on towers marching along the freeway) and this includes the scale at which we waste food. Studies (such as this NRDC study) show that not quite half the food we produce in the US is thrown away.

From the NRDC study:

“Getting food from the farm to our fork eats up 10 percent of the total U.S. energy budget, uses 50 percent of U.S. land, and swallows 80 percent of all freshwater consumed in the United States. Yet 40 percent of food in the United States today goes uneaten. This not only means that Americans are throwing out the equivalent of $165 billion each year, but also that the uneaten food ends up rotting in landfills as the single largest component of U.S. municipal solid waste where it accounts for a large portion of U.S. methane emissions. Reducing food losses by just 15 percent would be enough food to feed more than 25 million Americans every year at a time when one in six Americans lack a secure supply of food….”

[Given the population of the US, ‘one in six Americans’ is about 50 million people.]

Now even given that almost all of our energy systems exist at an industrial scale, there are some circumstances where smaller scale energy production makes sense: a farm, a homestead; the kind of place you have now, or (since you are reading this) the kind of place you may want to have, someday soon. For those situations, a local energy system providing all or some of your energy may make sense.

And in planning for that local situation, your situation, one of the first things you need to consider is matching needs to energy sources. Wind can be a great source of (intermittent) electricity. Direct solar is also good for electricity (PV), for space heating and hot water. But cooking presents a modest challenge for those two common local energy sources. You can make a solar oven— it’s pretty easy, really— but (begging the forgiveness of the solar gods) most solar ovens are kind of bulky and clumsy, don’t you think?

So here’s a twist: how about using wasted food to supply all of your cooking needs, and to supplement your space heating, or even hot water supply?

And how can you do that? (Gee. Somehow biogas comes to mind….)

Homemade Biogas

The short story is:

Start with a container. It doesn’t have to be strong, but it has to hold liquid, and gas at very modest pressures. The container can be steel, concrete, plastic or made of any other suitable material, with few exceptions. (Toxic stuff is not good; the biogas biology is sensitive.)

Get some organic material, of the kind we might use in making a compost pile. (Not woody stuff, but almost anything else. Food waste makes great biogas.)

Keep it wet, keep it warm, keep it pH-balanced, and very shortly, by a process that is natural, very ancient, and which may seem a bit magical (hey presto!) a burnable gas— biogas, made almost entirely from methane and carbon dioxide— will bubble out. (And just to clarify: methane is the main molecule in natural gas, the fossil fuel that is getting so much press nowadays because of fracking. Biogas gives you methane without the fracking. And it can even shrink your carbon footprint.)

There’s nothing else that’s essential, although lot’s more can be said about it. It really does not get any simpler for any kind of renewable energy use, except maybe standing in the sun to get warm, or burning wood. (Or eating. Definitely eating.)

It really is simple. Honestly. In fact, would you like some free plans for building any of four of the most common kinds of digesters? Then visit the free plans for biogas digesters page on the Complete Biogas website….

Of course, what you get out of your digester will be determined by what you put in. It has to be sized properly— and again, again, again, kept warm— but all else being equal, the more you feed it, the more gas will be produced.

Realizing this, you may well want to ask: How much food waste should I put in the digester? And what size should that digester be so that I can cook my meals, and get light in the evening?

And booyah, while we’re at it: How about the holy grail of biogas? Can I run my car on biogas?

Well, friends…. That’s all going to be discussed in the next blog… Keep reading.

A biogas plant installed at a house in Coimbatore, Tamil Nadu. Photo: S. Siva Saravanan” Or one might say: Feeding an ARTI-style digester with a floating gas holder.

Source: The Hindu (newspaper), “Cost effective green fuel for the kitchen


Small Scale Biogas Generator

There’s a gold mine out back of your local restaurant.

…Or at least that’s one way of looking at it. Of course, what I’m talking about is wasted food — the stuff you don’t eat from your plastic tray of super-sized this and that, the French fries that got a little too brown in the fryer, the stale burger buns. That stuff. It’s gold, really.

As my good friend Bob Hamburg of Dragon Husbandry once said:

“As for ‘waste disposal,’ we’ve got two mis-defined terms mashed together, resulting in an abominable oxymoron. In nature there is no such thing as waste. All residues serve as resources for further growth — there is nothing to be disposed of. Nothing is thrown away. Indeed, there is no ‘away.’ Everything must go somewhere. The misconception of ‘waste disposal’ must be superseded by a better understanding of ‘residue management.’”

Right on, Bob.

But hey, look at the stuff in that trash bin: It’s gooey. It’s gross, right? Who really wants that stuff, anyway? Well, maybe you will, when you see the whole picture.

Waking Up to Nature’s ‘Waste’ Management

It all grows out of standard ecology, the way the planet deals with energy and information (and the way we will, too, once our species gets past adolescence). Sunlight enters the atmosphere and makes green things grow: The largest usable bank account of stored solar energy on the whole planet is the set of green growing things, all the way from algae to giant sequoia. And a small fraction of that green riot is harvested to feed us and our animals.

Now in our (present, soon to be superceded; have faith) way of doing it, plant resources all go into factory-type buildings and come out as packages. Then, the packages are opened, we prepare food and eat it, and all that packaging trash is thrown away along with the food we don’t eat: more wasted food. We send it all to landfills or incinerators, go to sleep, wake up (sort of) and do it all again.

In nature’s way of doing it, just like Bob said, there is no “waste.” Ecological scientists talk about “trophic levels,” which in part is a way of saying that whatever one living thing leaves behind, another living thing uses as a source of energy. Plants consume sunlight, air and soil to produce green matter to feed vegetarians, such as cows or caterpillars. Vegetarians consume green matter to produce flesh to feed carnivores, such as wolves or people (or birds that eat caterpillars). And when anything once alive dies, then (if there is enough moisture available) the remains feed arthropods (little bugs), fungi, and a seething mass of microscopic life: nature’s compost pile.

This is the picture of the energy of life being shared among all living things, in a kind of sacred dance, happening all around us and unseen by most. The threads of the complex web of life are each connected to each — except where they are broken by the ignorant actions of man.

Stored Solar Energy

But hey. Too serious, right? Sure. But even still, that’s what we should maybe see when we look at that food behind the restaurant. Gooey? Well, that’s one way of seeing what’s there.

Yet maybe one of the wisest ways of seeing what’s there is to think about all that energy tied up in the carbon bonds of that food: the stored solar energy that can help you cook your own food, make great compost for your garden, and even heat your house, if you have enough of it.

How can this energy be put to use? Well that’s a story for part two.

Photo: Matt Steiman’s hand (Matt is Assistant Manager, Dickinson College Farm and Project Support, Dickinson College Biodiesel) pointing out a feature of the 3-year old EDPM plug-flow digester inside a greenhouse at the Dickinson College Organic Farm. Matt says: “We are making plenty of gas for cooking at the intern kitchen…. Currently we transfer gas from storage near the biogas digester to our kitchen using inner tubes that we fill from a manifold attached to our gas measuring drum. The 100-liter tubes are weighted at the kitchen and provide enough gas to cook a meal or two on our single Chinese burner.”


Solar Panel on Roof of House

When I retired from my faculty position at the University of Maine in 2003, I resolved that one of my retirement projects would be to greatly reduce my carbon footprint by making my home and transportation more energy efficient, and reducing my consumption of fossil fuels.  My wife, Lee, supported me in this undertaking, as we were very much aware of the terrible impacts on the environment of fossil fuel extraction, processing, and transport, and the pollution and climate change caused by the combustion of these fuels.   Our fellow humans and other living things depend on this environment, and it our responsibility to avoid harmful impact to them. We didn’t dream at the time that ten years later we would be powering our home and our local transportation largely with solar energy.

We decided to spend a substantial part of our savings and retirement income on this effort to reduce our carbon footprint. We were greatly helped by the residential energy and clean transportation income tax credits provided by the federal government, and the rebates from Efficiency Maine for purchasing and installing equipment in our home to increase energy efficiency and reduce carbon emissions. I am hoping that this essay encourages readers to do some of the same things we did within their financial means.  

As one’s geographic location and living situation have much to do with energy conservation, first I’ll tell you that I live at the end of a dead end, country road in Orono, Maine. Our closest neighbor is about a half-mile away. Our 2,200 square ft, single-story home sits near the top of a gentle slope at the head of a hay field, is sheltered by a forest on one side, and by a row of trees on the other side. Behind the house is our vegetable garden. We are fortunate in being only 3 miles by road to downtown Orono, a town of about 10,000 persons, and a mile further to the University of Maine, and only 6 miles to downtown Bangor, a small city of about 33,000 persons with good shopping areas and other amenities.

Before describing the steps we took to make our transition from fossil fuel to solar energy, I must point out that our transition is not complete. Each year we have been taking one or two long trips by fossil-fuel-powered car or coach and/or airliner, and much of what we buy including most of our food (we garden-produce some) and even the energy-saving equipment we have installed in our home is produced and shipped using fossil-fuel energy. We can and will take further steps to reduce our carbon footprint, but life completely without fossil fuels may not be possible in our economy without full withdrawal from it, and a return to a pre-industrial revolution life style. 

Here are the major steps in our transition (there were also smaller steps, too numerous to mention here):

• Early in the transition we reduced heating oil consumption with supplemental wood heating.
• We installed a solar domestic hot water system.
• We added more home insulation, and “sealed the cracks.”
• We installed a geothermal heat pump system for all home heating and cooling.
• We replaced our oldest all-gasoline car with a hybrid car with much lower gasoline consumption.
• We installed a solar electric (PV) array large enough for all home needs including the powering of the heat pump and an all-electric car.
• We replaced our next oldest all-gasoline car with an all-electric one with no gasoline consumption.   We charge this car’s battery with solar energy, and now use it for almost all of our local transportation.

As I describe each of these steps, where feasible I will indicate the financial costs, and the number of years it will take to pay off these costs from increased efficiencies and reduction in fossil fuel purchases.  Since we installed our new energy systems some of the prices have come down, and now low interest financing is available for some of them, making it possible for younger couples and others lacking our financial resources to take some of the steps we did. First, let me show you a diagram that explains how our new energy systems fit together.

We started in a small way well before retirement by reducing our heating oil consumption with supplemental wood heat, namely with a small wood stove in our living room, as many Mainers do. To distribute this heat to other parts of the house I installed an oscillating fan high on the living room wall, and directed its range to include both corridors leading to other parts of the house. By burning about one cord of oak wood a year, we reduced fuel oil consumption by about 20 percent, for a saving after fuel wood and electrical (fan) costs of about $350 per year, not to mention the comfort of a toasty warm living room. In recent years we have ceased using the wood stove because of the effects of old age on our ability to haul fuel wood.

We had been producing our domestic hot water by the same oil furnace/boiler that heated the house.  In 2007 we further reduced fuel oil consumption by installing solar water heating arrays on our south-facing roof, at a net cost after a rebate of $8,395. However, despite the 80-gallon hot water storage tank, we haven’t had quite enough solar heated water to last through occasional periods of extended cloudiness or when multiple houseguests are taking hot showers the same time of day. Therefore, a small percentage of heating of domestic hot water continued to be by fuel oil.  Nevertheless, the reduction of fuel oil purchases has been saving us about $875 per year, for a pay off period of about 10 years. We’re now more than half way through that period.  Today it is possible to set up a 12-year loan at 2.99% interest for a similar installation for a monthly payment of $75, and a return on investment (R0I) of 10.4 percent.   

At about the same time, we arranged for an energy audit of our then 35 year-old house to learn where we were losing most of our heat in winter, and then we went about sealing and insulating numerous places.   In 2008, we installed about two feet depth of blown fiberglass over the ceiling of our home to increase the ceiling R value to 60.  We could immediately feel the difference. In 2010, we installed three inches of foam insulation in the basement, from the underside of the ceiling and down the inside of the concrete foundation to 2-3 feet below the level of the exterior soil surface. The basement and the upstairs floors became noticeably warmer in winter.  The cost of all this work after rebates was $2,407. I’ll not attempt calculation of the payback period for this expense due to the complications caused by our switch in 2009 from heating with oil to a geothermal heat pump, and starting in 2012 by the powering of the heat pump with electricity from our own solar panels.


Slinky in Trench

In 2009 we replaced most of our remaining fuel oil usage with a geothermal system, namely, a heat pump in our basement, and heat exchange pipes outdoors and underground.  Six-thousand feet of polyethylene pipe, coiled like a stretched out slinky into three 200 feet long, six foot deep trenches extend under the field in front of our house. By 2011, no surface evidence of the presence of these trenches could be seen. Two small electric pumps in the basement circulate an antifreeze solution in this closed system of pipes, and to the heat pump. In the heat pump, heat is extracted from the solution to heat the house in winter, and heat is added to the solution to cool the house in summer. By pumping the solution around the pipes, this heat is transferred from or to the ground in the respective seasons. At the heat pump, the heat is transferred to or from a forced air ventilation system, heating the house in winter, and cooling it in summer. The heating phase uses the solar energy stored in the ground during the warm time of year, so fundamentally this is a solar system. The system has supplied our entire house heating and cooling since installation. 

Subsequently, we connected the heat pump to our domestic hot water system to use waste heat from the machine’s operation to supplement water heating. Since this system went into operation in August 2009, we have used only about 50 gallons of fuel oil per year for backup hot water heating during cloudy periods, and when we have multiple overnight houseguests. The net cost after a rebate and a federal tax credit for the geothermal heat pump system was $25,495. The replacement of oil house heating and the augmentation of hot water heating replaced about $2,900 worth of fuel oil per year, for a payback period of just under nine years.  Since we installed our geothermal heat pump, much less costly ductless mini-split air-based heat pumps have become practical for supplemental heating/cooling in this climate. They are mounted on outside walls, and are effective for heating and cooling home spaces similar to those that would be heated by an outside wall-mounted propane heater. They are electrically powered, much more energy efficient and cheaper to run than propane heaters, but not as efficient in BTU per dollar in our cold winter as geothermal systems.  

Although our heat pump system nearly ended our fuel oil purchases, it increased our usage of electricity by about $1,000 per year, and that leads me to the next part of the story. Most of the electricity we had been purchasing from the power company had been produced by fossil fuels, negatively impacting the environment. In 2012 we were able to further reduce our carbon footprint by installing solar photovoltaic (PV) panels to produce our own electricity, and by that September we were on line. We installed a 9.36 Kw PV array of 39 panels. Based on our history of electric usage we calculated this array would be enough for all our household needs including the heat pump plus the charging of an all-electric car for 7000 miles of local travel per year. As our south-facing roof was inadequate for this size array, and was already partially occupied by solar hot water panels, we installed a freestanding PV array in the field below our house.    The entire cost of this installation was $28,790 after a rebate and tax credit.  Based on our predicted electricity usage, and current power company rates (equivalent $2400 in annual electric savings), it will take us 12 years to recoup these funds. If power company rates go up, as seems likely, the time will be shortened.   Today it is possible to set up a 12-year loan at 2.99% interest for a similar installation for a monthly payment of about $240, and a return on investment (R0I) of 7.8 percent. Maine is presently lacking a rebate for solar PV installations. If it is returned, these figures will improve.

Producing one’s own solar electricity is complicated by the fact that the sun doesn’t always shine. There are two ways of handling this problem. The first is to install a bank of large and expensive storage batteries in one’s basement to charge up when the sun shines, and to draw electricity from them when the sun is not shining. This is the only option when one’s house is in a remote location off the electrical grid. A more practical and much less costly solution is the one we use.  Our solar array is connected to the grid power line just below our house, and thus we cogenerate electricity with the power company. We meter our solar electricity output to the grid, and separately meter the electricity we draw from the grid at our house.   When we produce more kilowatt-hours (KWH) than we use, as in April through October, the power company credits us for the excess KWH.  When we use more than we produce, as in November-March, we use up our credits. Our goal was to make our solar array barely large enough so that over the year we would wind up not having to buy electricity from the power company. In its first year of operation, the array produced 12,000 KWH of electricity, and is well on its way to producing about the same amount in this second year of operation. With the recent addition of an electric car, we will need another year of experience to see how close we have come to our goal.

Solar Panels

The final part of my story deals with my concern over the use of fossil fuel by our two cars.  I should explain that with our busy lives, and Lee’s and my involvements in different community projects and other volunteer work we have felt a need for separate cars. At our rural location, public transportation is inadequate to get us where we need to go in a timely manner. In 2010, we owned 1987 and 2002 Toyota Corollas, both getting 30-35 miles per gallon (mpg).   The 1987 car was ready to junk and recycle, so in 2010 we replaced it with a new Toyota Prius. With this hybrid car, we have since achieved the following approximate average numbers of mpg of regular gasoline:  winter local 45 mpg, highway 55 mpg; summer local 52 mpg, highway 57 mpg. Spring and fall have yielded intermediate values.  Like all vehicles powered entirely or in part by gasoline, mpg is determined by many factors including driving style. It takes practice, but we have found that slow acceleration, coasting to stops (when traffic allows), timing traffic lights to avoid full stops (when traffic allows), and consistently staying within posted speed limits considerably increase mpg.  Unfortunately, this is not the predominant driving style in our area and elsewhere. Since buying the Prius, we have purchased about 850 fewer gallons of gasoline than we would have purchased for the old Corolla, saving about $3,000, and emitting much less carbon and other pollutants to the atmosphere. By the end of 2015, we will have recouped the increased purchase price of a new Prius over a new Corolla by reduction in gasoline purchases (assuming similar mileage driven).

By November 2013, we were ready to replace our second old Corolla, for the final big step in our energy system. We were burning about 300 gallons of gasoline a year in our 2002 Toyota Corolla and 2010 Toyota (hybrid) Prius, combined. We sold the Corolla, purchased a new all-electric Nissan Leaf, and installed a 240v charging station for the Leaf in our garage. We now plan our local trips to minimize use of the Prius for local travel, and have been able to use the Leaf for over 90 percent of these short trips. The Leaf’s average range between charges is only about 95 miles, about 20 percent more in summer and less in winter. Apart from that limitation, it is a silent joy to use, much simpler and cheaper to run than a gasoline powered vehicle as it has no exhaust system, no gas tank and tank fill-ups, no engine oil to change or cooling water to monitor, and is easy and quick to plug in for battery charges.  A total charge at our station takes 2-3 hours, which we typically do overnight. At a quick charge station it takes only about a half hour, but such repeated quick charges sacrifice battery life.  

Given the range limitation of today’s all-electric cars, and the absence of quick-charge stations at convenient locations along most of the US highway system, these cars are not for everyone. Location of residence is an important consideration. They are most practical for use where most trips are short, as for well-placed rural locations like ours.  A large majority of our local trips for shopping and other activities are within 10 miles of home, with some up to 25 miles from home. These cars are also practical for persons with short daily commutes by car to work. Longer commutes are possible if a charging station is available at the destination, as is provided by some industrial and commercial employers. The availability of a second family car that can run on gasoline for the occasional longer trip adds additional practicality to all-electric car ownership. We still need to use our Prius hybrid for those trips. 

Since the November 2013 purchase of the Leaf, and as of August 2014 we have bought only about 75 gallons of fuel for the Prius to cover our three trips to Massachusetts and the occasional use of our two cars simultaneously for local trips. The cost of the new Nissan Leaf plus charging station, after subtracting the sale proceeds of the old Corolla, and receipt of a federal tax credit was  $25,804 or about the same cost of a new Prius. But the zero-emission Leaf is far superior economically because it is much less costly to run per mile.

I hope that all of the above encourages readers of this article to take some of the same steps we have taken to reduce their negative impacts on the environment. Each reader has unique considerations in deciding which steps to take. Any of the steps will help to reduce the terrible impacts on the earth and fellow human beings of fossil fuel extraction and use.  As mentioned earlier, younger persons than ourselves, and others who lack the money up front for some of these steps, can now obtain low interest loans for some of the home improvements including solar, and can obtain no- or low-cost financing for hybrid and electric car purchases. Solar array rentals have become a popular approach for going solar, but the jury is still out regarding whether rental or financing is more cost-effective.  

I would be happy to discuss how you, too, can reduce your carbon footprint. I can be reached at 207-866-4785 or at I am not associated with any manufacturers, vendors or installers of these products, and have nothing material to gain from sharing my experiences with you, and discussing how you may be able to take some of the same steps that Lee and I have taken.


Switchgrass Growing in the Field

Farmers and landowners want to lower fuel and feed costs, explore feed and fertilizer co-products, be more self-sufficient, and rely less of fossil fuels. Biomass grass crops can be established on marginal lands and processed as a fuel replacement for heating oil or propane, or as an addition to wood chips or pellets.

There are four main models for implementing grass energy on a farm. The models differ from each other in where the grass is grown and processed. Two are closed-loop models, in which the grass is grown and processed on-site, and the others are variations of processing the grass in a central facility and distributing production of the feedstock among regional farms.

Grass fuel can occur as bales that get chopped just prior to combustion or densified fuels like pellets, cubes, or briquettes. The densified fuels are made using machinery that applies high temperature and pressure to the chopped feedstock, pressing it into the desired shape. A series of dies and knives are responsible for cutting the fuel into its desired shape. Each of the four grass energy models, described below, produce one or two of these types of fuel.

Switchgrass Growing at University of Vermont
Switchgrass growing at the University of Vermont Horticulture Farm in South Burlington, Vermont. Credit: Vermont Bioenergy Initiative 

Closed Loop-No Processing: Grass fuel is grown on-site where it will be processed for heating fuel. The grass is harvested as usual, and stored and burned as bales. This requires a specific heating appliance designed to burn whole bales and significant storage space for the bales. While it is not economical to transport bales over great distances, this model can work among neighbors. For example, a school or prison with this heating system can contract with a neighboring farmer to produce the fuel bales. 

Small-scale On-Farm Processing: Grass is grown on-site where it will be processed. Stored bales are chopped in a hammermill and the grass is put through a small pelletizer or briquetter. The processing equipment can be stationary on the farm or mobile, moving between multiple farms. The pellet or briquette fuel can be used on the farm, such as in a biomass-heated greenhouse or chicken house, or it can be sold to neighboring users. The fuel produced is only suitable for commercial and industrial applications, and will not work well in residential heating appliances.

Regional Processing: Grass is grown within a 50-mile radius of a central processing facility that converts bales of grass from multiple farmers into briquettes. The processing facility should be co-located with a large heat load, such as a medium to large school or hospital, or even several buildings that will all be using grass fuel. 

Consumer Pellet Market: Grass is grown by contracted farmers within a 50-mile radius of the pellet mill. The mill produces standard pellets for the residential and small commercial markets.

From the farmer’s perspective, all four models described above involve growing the grass. The difference lies in whether the farmer will be contracting with a centralized processor or doing their own processing, and in the latter case, whether they plan to use the fuel on-site or market it to other customers. The key to success for these models is to match the fuel produced to the needs of the user. For example, Vermont Technical College in Randolph, Vermont, heats part of the campus with a pellet boiler, so the school’s farm operation uses a mobile pelletizer to process grass from their fields into pellet fuel.   

Much is known in the northeast Unites States about growing grass and a number of variety trials conducted around the region have pointed to certain species, like switchgrass, giant miscanthus and reed canary grass, as options that are highly productive and do well in this region. Grass stands are currently planted at the University of Vermont Horticulture Farm in Burlington and Vermont Technical College, and on several private farms like Borderview Farm in Alburgh and Meach Cove Farms in Shelburne. A collection of reports and guidelines for growing grass in the northeast is provided by the Vermont Bioenergy Initiative.    

A key aspect of grass energy development is to install grass-fueled heating appliances on farms and in schools or other municipal buildings, institutions and commercial settings while also producing grass fuel. For these institutional and small commercial heating systems, grass pellets, briquettes, and whole bales could be used for fuel. Depending on the type of system installed, the processing equipment should produce whole bales, pellets or briquettes to match the fuel needs. Mobile pelletizers and briquetters, like the one in development by Shelburne, Vermont-based Renewable Energy Resources, could be a good match, or in the case of whole bales, standard grass harvesting equipment would be used to produce fuel.

Switchgrass Harvest
Switchgrass being harvested at Meach Cove Farm in Shelburne, Vermont. Credit: Vermont Bioenergy Initiative

While growing the crop and producing the fuel can be relatively straightforward, there are not currently extensive markets for the fuel. This presents a chicken-and-egg problem for the farmer and their potential customers. Farmers are hesitant to grow a crop with an uncertain market, and building owners and municipalities are not likely to install a heating system for which they can’t find a reliable fuel source. Close cooperation between fuel suppliers and customers is important, and long-term contracts can help build confidence between partners. 

There are also alternative markets for grass crops that can be used in the interim while a fuel market is established. These alternatives include fiber for paper products, animal bedding, compost for mushroom growers, resin in particle board, absorbents for environmental clean-up, and dairy rations. Additionally, the fields themselves have value as wildlife habitat and stream buffers that prevent erosion and remove nitrogen and phosphorous from farm run-off. These alternative uses for grass are discussed in more detail in the report, “Grass Energy in Vermont and Northeast.”

Miscanthus Second Year Growth
Miscanthus in its second year at Meach Cove Farm in Shelburne, Vermont. Credit: Vermont Bioenergy Initiative

An important consideration for growers is the economic feasibility of growing grass for fuel or alternative markets. Dr. Sid Bosworth, researcher and professor at the University of Vermont School of Agriculture and Life Sciences, has developed a grass energy cost estimator to determine the per-ton cost of production, located on his website. By comparing the cost of production to market prices, a grower can determine whether producing and selling grass fuel makes financial sense.

Considering additional benefits to the farm can be helpful, too. For example, using grass to help clean up runoff from the farm, thereby helping to clean up local waterways, can be a valuable marketing asset. Improving wildlife habitat with grass crops, conserving open land, and utilizing marginal soils are additional benefits. It’s hard to put a dollar value on land stewardship, but these are services to both the longevity of a farming operation and to the greater community.

Photo by Fotolia/nspooner

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