Crop residues, often termed waste, are in fact a vital component of soil agro-ecosystems. Crop residues contain substantial amounts of plant nutrients (primarily calcium, nitrogen, potassium, phosphorus and manganese). If these residues were harvested every year, these nutrients would have to be replaced by increased fertilizer use.
Many soil organisms feed primarily on crop residues, and they recycle nutrients, build soil organic matter and maintain soil organic carbon levels.
I envision a distributed network of small- to medium-scale pyrolizers scattered across the Midwest. Farmers will round-bale stover, leaving at least 30% of it on the field to protect the soil. The local pyrolyzer will burn the stover to produce biofuels, charcoal (biochar) and bio-oil. The bio-oil will be shipped to a local utility and burned to generate electricity.
The biochar may be injected into farm fields as a slurry in either in fall or spring. Farmers won't want to mess with biochar every year on every field, preferring to apply it to a given field once every 10 years or so, possibly blending it with manure. They may target its application to sandy or marginal soils, where biochar can boost productivity the most.
I hope that the biochar will either increase yields or reduce input costs by making nutrient and water use more efficient. Biochar will dramatically increase soils' organic carbon content, fertility and largely eliminate the need for liming.
Local streams will be cleaner due to biochar's retention of soil nutrients and crop chemicals. And farmers will have carbon credits to sell for sequestering atmospheric soil underground, via the biochar. Crop residues are critically important for building and maintaining soil structure.
Biochar additions to soils will help maintain soil quality and productivity and therefore allow a larger portion of the corn stover for bioenergy production than would be possible without adding the biochar.
I propose a fundamental paradigm shift: integrated agricultural biomass-bioenergy systems that build soil quality and increase productivity so that both food and bioenergy crops can be sustainably harvested.
Pyrolyzers are relatively inexpensive and can be scaled from small to large to match local sources of biomass, thus minimizing transportation costs for bulky biomass.