Subject: Alkali in grasses Roger Samson (REAP-Canada) presented the results of work in Canada to reduce ash and alkali in grasses, particularly switchgrass, for use as fiber and fuel. His findings help to explain why, in 1992, we found decreasing chlorine and alkali in wheat straw as we moved north from the Mexican border and across different soil types. Reducing these elements should reduce deposition and make deposits easier to remove from heat transfer surfaces. It remains to be seen whether fuel and fiber uses can support the (20-25%) lower yield and spring harvest necessary to obtain lower ash and alkali. Benefits are likely to be site specific. Tom Miles Roger's Abstract from: BioEnergy ’98: Expanding BioEnergy Partnerships, Madison, WI Great Lakes Regional Biomass Energy Program <http://www.cglg.org/projects/biomass>http://www.cglg.org/projects/biomass COPYRIGHT 1998 STRATEGIES TO REDUCE THE ASH CONTENT IN PERENNIAL GRASSES Roger Samson and Bano Mehdi Resource Efficient Agricultural Production-Canada Box 125, Ste. Anne de Bellevue, Quebec, H9X 3V9, Canada REAP@interlink.net ABSTRACT Perennial grasses have been identified as the lowest cost dedicated agricultural feedstock for energy and agri-fibre markets. However, it is of paramount importance that the ash content of these feedstocks be reduced so as to facilitate their commercialization. High ash contents are particularly troublesome for achieving efficient combustion when used for bioenergy applications, and in chemical recovery systems, in the pulp and paper industry. The major component of ash is silica. Warm season (C4) grasses are found to have lower silica levels than C3 grasses owing primarily to the fact that they utilize water 50% more efficiently. Silica levels in grasses are also highly influenced by the monosilicic acid content of soils. As a result, clay soils produce higher silica containing feedstocks than sandy soils. Silica levels are lowest in the stem fraction of grasses, and highest in inflorescences, leaves, and leaf sheaths. Selection for higher stem content will help to reduce the plant’s ash content, while increasing the desirable feedstock characteristics, such as cellulose content, which is important for ethanol and pulp and paper markets. Reducing the potassium and chlorine contents of feedstocks grown for fuel purposes is important to improve combustion efficiencies. The chlorine content of feedstocks is strongly influenced by fertilization practices and can be minimized by using chlorine free fertilizers. Potassium and chlorine contents can be reduced to similar levels as wood chips by overwintering the grasses, however, there is a trade off in that lower yields are harvested. The feedstock production cost of overwintered switchgrass is lower than short rotation forestry, and switchgrass provides similar properties for combustion as wood. ------------------------------------------------------------------------------ Thomas R. Miles tmiles@teleport.com Technical Consultants, Inc. Tel (503) 292-0107/646-1198 1470 SW Woodward Way Fax (503) 605-0208 Portland, Oregon, USA 97225 Bioenergy List SPONSORS and ARCHIVES: http://solstice.crest.org/renewables/bioenergy-list-archive/