COMBUSTION FUEL PROPERTIES OF MANURE AND COMPOST FROM PAVED AND UNPAVED CATTLE FEEDLOTS AS MODIFIED BY ANNUAL PRECIPITATION
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Research was conducted to determine the effects of feedlot surfacing materials (soil/unpaved vs. fly-ash paved), partial composting and/or storage in windrow or greenhouse, and wet year (2005) vs. dry year (2006) feedlot conditions on cattle feedlot biomass (FB) characteristics pertinent to combustion or gasification processes involving reburn or co-firing with coal or lignite as described elsewhere. Bulk quantities of FB were harvested from 12 fly-ash paved pens and six soilsurfaced pens in a 400-head research cattle feedlot near Bushland, Texas. FB was windrow-composted, and samples were analyzed using proximate, ultimate, and elemental ash analyses. Higher heating value (HHV) before composting (termed raw manure, RM) was significantly higher for FB harvested from paved pens (termed low ash, or LA-FB) vs. soil-surfaced pens (termed high ash, or HA-FB) on a dry basis and dry ash-free (DAF) basis for both study years. Ash content (dry matter basis) was significantly lower and volatile matter (VM), carbon (fixed and total), and hydrogen were significantly higher for LA-FB (paved pens) vs. HA-FB (unpaved pens) for both years of the study. As-harvested HHV averaged 6,304 and 8,190 kJ kg-1 w.b. (2,710 and 3,521 BTU lb-1 w.b.) for HA-FB for the wet and dry years, respectively, and as-harvested HHV for LA-FB averaged 13,407 and 13,224 kJ kg-1 w.b. (5,764 and 5,685 BTU lb-1 w.b.) for the wet and dry years. Partial composting (PC) in windrows (for 51 to 55 days in 2005 or 91 days in 2006) reduced HHV w.b. by an average (both years) of 11.4% for the resulting HA-FB-PC and 14.8% for the resulting LA-FB-PC. The LA-FB-PC was significantly different from HA-FB-PC for all proximate and ultimate analysis parameters for both 2005 and 2006 manure, with the exception of 2006 wet-basis HHV. Heating value on a DAF basis averaged 20,984 kJ kg-1 (9,022 BTU lb-1) for LA-FB-PC and 18,941 kJ kg-1 (8,143 BTU lb -1) for HA-FB-PC. Greenhouse storage for 9 to 12 months of the 2005 harvested LA-FB-RM and LA-FB-PC preserved fuel quality better than did continuous storage of LA-FB-PC in a windrow, probably because lower moisture conditions were maintained under greenhouse storage conditions (7.7% to 13.4% w.b. final range) compared with uncovered windrow storage (17.4% final moisture content). Elemental analysis of ash from LA-FB was higher than from HA-FB for Ca, P, Cl, K, Mg, Na, and S, but was lower for Si, Al, Ti, and Fe without or with partial composting. Metal contents were similar for both high-ash and low-ash FB. 2013 American Society of Agricultural and Biological Engineers ISSN 2151-0032.
