I have access to lots of shredded black-and-white laser-printed office paper. I have read about using newspaper as mulch, but what about using office paper for mulch or composting?
Many people use shredded non-glossy paper in mulch or compost, where it typically degrades in a single season. Since paper is a wood product, you should regard it as a high-carbon soil additive, similar to sawdust. When using it to make compost, you will need to add plenty of nitrogen-rich green material. When using it as mulch, most gardeners cover it with a layer of organic mulch, such as leaves.
Laser printers use toner rather than ink, which usually contains plastics or waxes. The residual effects of toner in soil are unknown, but we do know that soil active with plenty of fungi and bacteria does an amazing job of breaking down some man-made chemicals. Still, if you want to grow the best possible food crops, avoid putting materials into the soil that are not natural, and bleached office paper, printed with wax or plastic-enhanced toners definitely falls into the unnatural category.
— Barbara Pleasant, contributing editor