Ensiled Pretreatment and Bioconversion of Corn Stover and Swine Manure

Grant# 02-1A
Principal Investigator: Thomas Richard
Organization: Iowa State University
Technical Area: Renewable Energy

This project will investigate anaerobic solid-state fermentation strategies for biomass pretreatment and conversion to sugars and organic acids. This effort will extend our very positive preliminary results developing biomass storage and bioconversion technologies suitable for multi-product manufacturing of biomass fuels, biochemicals, fiber, and other industrial feedstocks. In this project we will optimize a range of solid-state fermentation processes for both long-term storage and bioconversion to fermentable sugars and organic acids.

This study will investigate the use of amendments such as enzymes and chemical treatments for controlled storage and conversion oflignicellulosic feedstocks to energy and chemical products. Specific product streams examined will include organic acids, soluble sugars, and residual fiber. Biomass feedstocks will include corn stover (both with and without the brown midrib trait) and swine manure. Initial investigations will be in bench-scale experiments to allow large numbers of replications to optimize amendment rates. For the stover-manure mixtures, these bench-scale studies will be followed with pilot-scale experiments, using 20L anaerobic bioreactors to examine the impacts of sequential acid extraction on subsequent fermentation. These pilot-scale trials will be used to realistically assess the impacts of full-scale implementation on anaerobic process conditions, and to provide large quantities of materials for testing recovery technologies and product characteristics. Promising feedstock and pretreatment strategies, specifically the brown midrib trait in crop genetics and pretreatment with alkaline hydrogen peroxide, will be investigated to increase digestibility and conversion.

The proposed study will extend our successful preliminary research to further develop solid-state fermentation strategies for biomass storage and conversion. In each of the proposed experiments, we will address the impacts of fermentation on dry matter loss, structural polysaccharide fractionation, and fermentation products.

Project Objectives

Specific objectives for this project are:

1) Investigate the potential for enzyme amendments and methanogen inhibition to enhance solid-state fermentation of crop residue/manure combinations with respect to transformations of valuable chemical and lignocellulosic constituents in a sequential anaerobic fermentation.

2) Implement optimal pilot-scale fermentation processes as developed through objective 1, allowing sequential extractions of a) initial lactic or acetic acid dominated product streams, b) secondary fermentation products dominated by butyric and/or acetic acids, and c) assess their impact on biomass properties and product formation.

3) Evaluate the susceptibility of crop residue with the brown mid-rib trait to enzymatic pretreatments and subsequent impacts on the fermentation strategy and other bioconversion processes.

4) Investigate the potential of alkaline hydrogen peroxide as a pretreatment to enhance solid-state fermentation of crop residues and potential impacts on bioconversion of cell wall polysaccharides to organic acids.