Effects of Aeration and Covers on NH3, Water and Dry Matter Loss During Windrow Composting of Dairy Manure

Abstract

Modern dairy farms generally have two manure streams, solid and liquids. The solidmanures come from the maternity stalls and calf barns while the liquid manures (85-90% moisture)come from free stall barns. This paper reports results of controlled outdoor full scale windrow studiesunder Ohio's weather conditions using both the solid and liquid dairy manure waste streams. Studiesincluded: a) TW, turned windrows/ natural convection/ no cover, b) TWA, turned windrows/controlled aeration/ no covers and c) TWC, turned windrows/ natural convection/ covered. Volumeand weight reductions as well as dry matter, moisture and nitrogen losses during composting werepresented as functions of composting time. Results for dairy manure (free stall) mixed with sawdustor straw using the TW method showed weight losses and volume losses of over 80% the compostmix. Normalized to the original manure weights and volumes, reductions from composting were 77%w/w and 42% v/v with the sawdust amendment and 76% w/w and 57%v/v with the straw. TWAstudies using oxygen levels to set aeration patterns showed increases in total weight, water andnitrogen loss. Results on dry matter and C loss were inconclusive. Results for TWC studies showedcovering the windrow with a fleece blanket during composting reduce rates of dry matter loss andnitrogen. Over a 77 day composting period, %C loss was 54% versus 38 % while N loss was 18% to4% for uncovered vs covered, respectively. Results suggested that moisture loss would be increasewith covers. This result was believed due to covers shedding rainfall