J. Richard Hess

Physical Separation of Straw Stem Components to Reduce Silica

In 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 sources 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.

Fractionation of Higher Value Crop Residue Components for Conversion into Bioenergy and Industrial Products

Separation of biomass is generally done by air-based fluidized bed density separation nsystems. Although these separation systems are well proven for harvesting grain the ntechniques have not been directly applied to separating biomass subcomponents (e.g., stems, nleaves, etc.). Ultimately, a single pass harvesting operation for grain and select biomass subcomponents of crop residues is desirable. Our approach is to separate the desirable straw nstems from the undesirable leaves, sheaths, and nodes, since the fibrous straw stem contains nmuch less silica and waxy cuticle layer than do the leaves and sheaths. The leaves and nsheaths contain higher nutrient levels, so they would be better utilized as organic matter for soil nconservation. This separation will allow straw stem utilization in existing boilers for bioenergy nproduction or as a biomass source for numerous industrial products. We are evaluating ncombine harvester unit operations for biomass separation by instrumenting the internal noperating units of the harvester and collecting the experimental sensor data characterizing the nseparation. These data will allow us to quantify the extent and quality of biomass separation that ncan be obtained with existing threshing and separation unit operations with a range of biomass. nSecondly, from analyses of the partitioning of potassium, chloride, silica, total ash, and fines, nand recovery of usable fiber among the subcomponents of the residue, we have determined that nby harvesting only the stems, a higher value feedstock results.

Distributed fungal harvest of higher value wheat straw components

Each year, millions of tons of agricultural residues such as wheat straw are produced nworldwide. In this paper, we describe ongoing efforts to solve technological, infrastructural, and neconomic challenges to using this straw for bioenergy and bioproducts. Among these nchallenges, silica in straw forms a low-melting point eutectic with potassium oxide, causing nexcessive slagging deposits in boilers. The presence of chlorides causes corrosion beneath the nslag deposits on boiler tubes. Silica fouls kilns and fines slow paper machines, limiting the nusefulness of straw in linerboard production. Poor resin bonding to the waxy outer cuticle of the nstraw, poor resin penetration, and high resin consumption due to fines limit the use of straw for nstraw-thermoplastic composites and for straw particleboard. Poor cellulase penetration limits nthe use of straw for production of fuels (ethanol) and chemicals. Straw consists of stems, nleaves, sheaths, nodes, awns, and chaff. Not all parts of straw are equally valuable. The stems nare of higher relative value because they contain much less silica and fines. In contrast, the nother plant parts are of relatively lesser value because they are the principle sources of silica nand fines. Our approach to reducing silica content is to selectively harvest the straw stems nusing an in-field physical separation, leaving the remaining components in the field to build soil norganic matter and contribute soil nutrients. To address resin issues and cellulase penetration, nwe are developing distributed windrow system designs employing white rot fungi to upgrade the nstraw by selectively removing hemicellulose and lignin.