BIOENERGY BY-PRODUCTS AS ALTERNATIVE SOURCES OF PLANT NUTRIENTS FOR PRAIRIE SOILS

Abstract

Rapid growth in the bioenergy industry has created large amounts of the various by products associated with bioenergy production. A proper method of utilizing these by products has recently been sought, including their potential use as soil fertilizers or amendments. However, more knowledge is required to validate this option, as well as to make recommendations for their management. The objective of this research was to evaluate the effectiveness of bioenergy production by-products (BPB), mainly wet distillers’ grains (WDG), thin stillage (TS), glycerol (GL), biochar (BC) and ash, as sources of plant nutrients in prairie soils with emphasis on their impact on soil biological and chemical properties and processes. This was addressed through a series of growth chamber and field studies. Under controlled environment conditions, the WDG, TS and GL with urea nitrogen (N) fertilizer increased N2O emissions from soil, but not in excess of that produced from soil treated with urea alone. Microbial activity as indicated by emission of CO2 was also increased significantly by WDG, TS and GL with N. The WDG and TS increased nutrient ion supply rates in soil, owing to their high content of readily available nutrient. In general, soil enzyme activity (alkaline phosphatase, dehydrogenase, protease) was significantly increased by WDG, TS and GL addition. These by products also increased soil microbial biomass and microbial quotient with the exception of TS, likely related to its lower C content. Gasified dried distillers’ grainss ash (DDGA) was an effective source of plant available phosphorus (P) whereas gasified meat & bone meal ash (MBMA) had lesser effects on crop yield and P uptake compared to mineral fertilizer. The majority of P remaining in the soil following MBMA application was in stable and recalcitrant forms. In a two-yr field study, TS was an excellent source of nutrient in promoting crop yield and nutrient uptake that was greater than or similar to urea fertilizer, especially when injected. However, residual NO3--N and available P accumulated in soil after the second year of TS application. Amendment with BC and GL resulted in limited effects on crop yield and nutrient uptake, with GL tending to reduce crop yield and N uptake due to microbial immobilization. Overall, the BPB amendments can be of benefit by enhancing biological activity, nutrient availability and crop growth, although their effect is greatly dependent on the form and composition.