Ecological and Environmental Impacts of Bioenergy

Bioenergy systems and specific bioenergy projects can have positive and negative ecological impacts (the effects on ecosystems and species within them) and environmental impacts (effects on geophysical systems such as water and climate), and the overall net impact can be positive or negative depending on the particular system or project under consideration.  Specific impacts and net impacts depend on the feedstock type, biomass production system, conversion technology (i.e., transformation of feedstock into energy products), transportation/distribution system, and use or disposal of co-products and by-products, respectively.  As discussed above, life-cycle assessment is an important tool for understanding net impacts of bioenergy.

Many of the ecological and environmental impacts of bioenergy are associated with land use and land use change in connection to feedstock production.  Bioenergy-related land use decisions may affect local, regional and global ecological and environmental systems. The remainder of this section focuses on land use and land use change, and on other high-priority concerns, including GHG emissions, habitat change, biodiversity, soil quality, and water quantity and quality.

Land use and land use change

Land use decisions are affected by many factors, including public policy, prices of agricultural and forest commodities and petroleum (figure 3.3).  Profitability of specific land uses, non-economic benefits of alternative land use, and opportunity costs associated with competing land uses also   influence decision-making.  Decision-makers who choose to produce bioenergy feedstocks must consider land use and land use change.  Land use is management of land resources for economic benefit and includes tillage, maintenance and harvest activities as well as conservation practices.  Land use change (LUC) includes conversion of native ecosystems into agriculture use (i.e., land cover change), as well as switching from one crop type to another (or switching from one forest type to another).   Also included in the LUC category is diversion of food crops grown primarily for food to bioenergy feedstock use (e.g., corn grain).

Land use and LUC associated with bioenergy feedstock production can increase or decrease the direct, indirect and non-financial benefits of native and managed ecosystems. Native and managed ecosystems are a source of financial benefit for humans when materials are removed from these systems and exchanged in markets.  Native ecosystems and managed ecosystems also provide many benefits which indirectly affect human financial benefit.  Ecosystems provide many non-financial benefits as well.  Water and nutrient cycling are but two examples of the benefits ecosystems provide but for which there is no direct economic value.

Figure 3.3. Factors and their interactions influencing land use decisions. (CL Williams, 2011.)

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