Direct emission of methane and nitrous oxide from switchgrass and corn stover: implications for large‐scale biomass storage

Abstract

Little is known about the contributions of biomass feedstock storage to the net greenhouse gas emissions from cellulosic biofuels. Direct emissions of methane and nitrous oxide during decomposition in storage may contribute substantially to the global warming potential of biofuels. In this study, laboratory-scale bales of switchgrass and corn stover were stored under a range of moisture (13.0-32.9%) and temperature (5-35°C) conditions and monitored for O 2 consumption and CO 2 , CH 4 , and N 2 O production over 8 weeks. Gas concentrations and emissions rates were highly variable within and between experimental groups. Stover bales produced higher CO 2 concentrations (P = 0.0002) and lower O 2 (P < 0.0001) during storage than switchgrass bales. Methane concentrations (1.8-2100 ppm) were inversely correlated with bale moisture (P < 0.05), with emissions rates ranging from 4.4-914.9 lg kg À1 DM day À1 . Nitrous oxide concentrations ranged from 0 to 31 ppm, and emissions from switchgrass bales inversely correlated with temperature and moisture (P < 0.0001). Net global warming potential from each treatment (0-2.4 gCO 2 e kg À1 DM) suggests that direct emission of methane and nitrous oxide from aerobically stored feedstocks have a small effect on net global warming potential of cellulosic biofuels.

Diurnal pattern of nitrous oxide emissions from soils under different vertical moisture distribution conditions

“…The N2O emissions for all the SUW treatments showed a bimodal diurnal curve pattern on 22 April, 6 May, and 20 May with peaks appearing mainly at 12:00 and 20:00 h (Figures 1a, 1b, and 1c and Figures 3a, 3b, 3c, and 3d). It was confirmed that peak N2O fluxes frequently appeared when soil moisture was appropriate and the temperature was high (Qiu et al, 2011;Emery and Mosier, 2015;Trost et al, 2015). The maximum N2O fluxes on all sampling dates were 2242.6, 3261.0, and 2678.1 μg N2O m -2 h -1 for the SUW12, SUW15, and SUW18 treatments, respectively, which were measured on 17 June when soil WFPS at the 0-12 cm depth ranged from 45% to 64%.…”

Techno-Economic Assessment of a Chopped Feedstock Logistics Supply Chain for Corn Stover

“…The primary drawback of chopped logistics systems is that the transportation costs increase compared to bale systems, as trucks reach the maximum allowable load weights before volumetric capacity has been reached due presence of water, such that long distance transportation is generally thought to be cost prohibitive. However, chopped, wet logistics systems offer multiple advantages over bale systems primarily due to the fact that they have consistently and successfully demonstrated biomass preservation of >95% over 6-12 months compared to the 10-30% seen in aerobic systems (Smith et al, 2013;Emery and Mosier, 2014;Wendt et al, 2014Wendt et al, , 2018. Wet storage systems also reduce the fire risk relative to dry bales in storage and preprocessing.…”

Cattle Diets Strongly Affect Nitrous Oxide in the Rumen

“…To the best of our knowledge, possible CH 4 emissions from silages have also not been studied or discussed in literature. Emery and Mosier [21] measured GHG emissions from unfermented feedstuffs and detected small amounts of CH 4 ; however impact on the net global warming potential was assessed to be small.…”

“…Though, they also agree that more research is needed to better quantify that source of emission as formation in the rumen is questionable [20]. However, beside the ruminant itself, the forage used as feedstuff can also act as a source of emissions: for non-fermented forages Emery and Mosier [21] measured emissions of CO 2 , CH 4 , and N 2 O from switchgrass and corn stover under varying storage conditions. Both CH 4 and N 2 O were detected and concentrations were influenced by forage DM concentration.…”