Physical Separation of Straw Stem Components to Reduce Silica

Abstract

SUMMARYIn this paper, we describe ongoing efforts to solve challenges to using straw for bioenergy and bioproducts. Among these, silica in straw forms a low-melting eutectic with potassium, causing slag deposits, and chlorides cause corrosion beneath the deposits. Straw consists principally of stems, leaves, sheaths, nodes, awns, and chaff. Leaves and sheaths are higher in silica, while chaff, leaves and nodes are the primary source of fines. Our approach to reducing silica is to selectively harvest the straw stems using an in-field physical separation, leaving the remaining components in the field to build soil organic matter and contribute soil nutrients.

The Biorefinery Concept

“…Reducing the cost of collection, transportation and storage through pre-processing biomass into a higher-density, aerobically stable, easily transportable material is therefore critical to developing a sustainable infrastructure capable of working with significant quantities of raw material [52]. The most common approach used to increase biomass density is grinding.…”

“…Pre-processing might be performed onsite but can also be done during harvesting. An example of technology recently developed to address the engineering challenge presented by low-bulk-density biomass such as wheat straw is a multi-component harvester that can simultaneously and selectively harvest wheat grain and the desired parts of wheat straw in a single pass [52].…”

The Biorefinery Concept–An Integrated Approach

“…Reducing the cost of collection, transportation and storage of biomass through densification is thus critical to developing a sustainable infrastructure capable of working with significant quantities of raw material (Hess et al, 2003). In addition, the economics of many conversion processes, which are batch operations, would be dramatically improved through an increase in density, as the inherent low density of biomass limits the amount of material that can be processed at any one time.…”

“…Pre-processing might be done 'on the farm', but can also be done during harvesting. An example of technology recently developed to address the engineering challenge presented by low bulk density biomass such as wheat straw, is a multicomponent harvester, which can simultaneously and selectively harvest wheat grain and the desired parts of wheat straw in a single pass (Hess et al, 2003).…”

Distributed Physical and Molecular Separations for Selective Harvest of Higher Value Wheat Straw Components Project

“…To better handle the straw for the laboratory studies, the large bales were rebaled as needed into smaller 0.61 m x 1.2 m (2 ft x 4 ft) bales containing about 22.7 kg (50 Ib) each, and placed in covered storage. To remove the plant components that are the sources of high surface area fines (leaves, sheaths, nodes, and fines), the straw was rethreshed before use as described by Hess et al (2003). Only the separated straw stems were used in the laboratory studies.…”