An overview of biogeochemical issues related to bioenergy production

Biomass production for bioenergy can affect biogeochemical processes by increasing the demand on soil nutrients needed to sustain site productivity because of incrementally greater removals of organic matter than would occur for traditional crop management, which in turn affects soil organic matter and associated carbon and nutrient storage and cycling. Management for feedstocks can affect soil physical, chemical and biological properties, but impacts can be mitigated through appropriate management.

Biogeochemical cycles related to feedstock production are also affected by over-arching issues such as increased atmospheric CO₂ concentrations, climate change, atmospheric deposition of nutrients, possible future scarcity of minerals used in fertilizers, and land use and land cover changes associated with establishing crops that supply feedstocks for bioenergy; the effects of impacts associated with these issues can also be cumulative.

Feedstock production can also have off-site impacts that include GHG emissions, eutrophication, and disposal of by-products at the end of the life cycle. Off-site impacts are not all negative: ash can be used to replenish some soil nutrients, biochar can improve soil quality, and some bioenergy processes (e.g., anaerobic digestion of manures) can be used to reduce GHG emissions and nutrient loading of the environment.

We will review the various biogeochemical issues that are relevant to bioenergy feedstock production, and provide some thoughts on future directions.