Miscanthus and switchgrass feedstock potential for bioenergy and carbon sequestration on minesoils

Greenhouse Gas Emissions following Conversion of a Reclaimed Minesoil to Bioenergy Crop Production

“…It is unclear why the highest N 2 O–N emissions occurred under miscanthus at the medium effluent application rate, and not at the higher application rates. Probable reasons for this include lower plant uptake under miscanthus during the first year of establishment compared with that under the maize and meadow land uses (Lewandowski & Schmidt, ; Dohleman et al, ), the inherent variability of minesoils (Guzman & Lal, ), and the difficulty of applying consistent rates of effluent. With the exception of the miscanthus land use with medium rate of effluent, the fraction of applied N lost as N 2 O–N across land use and effluent application rates was on average 1·4%.…”

“…The highest CO 2equ values occurred under the maize land use, which on average across effluent application rates were 6·6 CO 2equ Mg ha −1 y −1 , and miscanthus land use with medium effluent application rate at 7·1 CO 2equ Mg ha −1 y −1 . It is expected that biomass production under miscanthus land use will significantly increase in the coming years, with many studies estimating C inputs from 6 to 20 Mg C ha −1 y −1 once established on marginal lands (Guzman & Lal, ). If miscanthus biomass yields trend to the higher end of these estimates, this would offset the first year's C debt relatively quickly and result in a future net sink for GHG emissions.…”

“…In terms of GHG mitigation, many studies have shown that biofuel feedstock production under perennial C 4 grasses such as miscanthus ( Miscanthus × giganteus ) and switchgrass ( Panicum virgatum L.) has a much larger CO 2 sink potential and lower GHG emissions when compared with annual crops and C 3 grass systems in the USA (Qin et al, ). This is in large part due to miscanthus and switchgrass, both having a much larger soil organic carbon (SOC) sequestration potential via CO 2 capture by photosynthesis and storage of C in the soil (Shrestha et al, ; Don et al, ; Guzman & Lal, ). Reported estimates of net GHG equivalent emissions under miscanthus land use range from −5 to 0·3 Mg CO 2equ ha −1 y −1 (Cherubini et al, ; Davis et al, ; Bonin & Lal, ) and −0·5 to 11 Mg CO 2equ ha −1 y −1 in maize land use systems (Adler et al, ; Bonin & Lal, ; Guzman et al, ).…”

“…Perennial grasses, which have low maintenance and nutrient requirements, yet produce high biomass yields such as miscanthus, switchgrass, and some prairie grasses, have been suggested as having the highest potential for bioenergy production on marginal lands (Guzman et al, ; Skousen et al, ). However, biomass productivity on marginal lands varies drastically owing to specific interactions between soils and climate conditions and management practices, which must be evaluated on a regional basis (Guzman & Lal, ).…”

“…Therefore, the objectives of the present study were to measure annual GHG (CO 2 , N 2 O, and CH 4 ) emissions and the principal controls (i.e., soil temperature and moisture) on a reclaimed minesoil under antecedent meadow and land use changes to miscanthus and maize production. Studies have shown that land use changes from meadow to miscanthus and maize production can result in net GHG emissions, owing to depletion of SOC (via CO 2 from microbial respiration) and lower atmospheric CO 2 sequestration because of decline in biomass production during the first year of establishment (Guzman & Lal, ; Ussiri & Lal, ). In order to aid in offsetting some of this expected net GHG emissions due to land use changes, effluent was added from a nearby methane anaerobic digester, which uses primarily sewage sludge and food wastes as their primary C substrate.…”