Carbon and nitrogen dynamics in bioenergy ecosystems: 2. Potential greenhouse gas emissions and global warming intensity in the conterminous United States

Abstract

This study estimated the potential emissions of greenhouse gases (GHG) from bioenergy ecosystems with a biogeochemical model AgTEM, assuming maize (Zea mays L.), switchgrass (Panicum virgatum L.), and Miscanthus (Miscanthus 9 giganteus) will be grown on the current maize-producing areas in the conterminous United States. We found that the maize ecosystem acts as a mild net carbon source while cellulosic ecosystems (i.e., switchgrass and Miscanthus) act as mild sinks. Nitrogen fertilizer use is an important factor affecting biomass production and N 2 O emissions, especially in the maize ecosystem. To maintain high biomass productivity, the maize ecosystem emits much more GHG, including CO 2 and N 2 O, than switchgrass and Miscanthus ecosystems, when high-rate nitrogen fertilizers are applied. For maize, the global warming potential (GWP) amounts to 1-2 Mg CO 2 eq ha À1 yr À1 , with a dominant contribution of over 90% from N 2 O emissions. Cellulosic crops contribute to the GWP of less than 0.3 Mg CO 2 eq ha À1 yr À1 . Among all three bioenergy crops, Miscanthus is the most biofuel productive and the least GHG intensive at a given cropland. Regional model simulations suggested that substituting Miscanthus for maize to produce biofuel could potentially save land and reduce GHG emissions.

Nitrogen fertilizer and landscape position impacts on CO2 and CH4 fluxes from a landscape seeded to switchgrass

“…Concerns about global warming and dependence on foreign fossil fuels in the United States triggered a search for more sustainable sources of energy (Congress, ; Bang, ). US legislators mandated production of at least 36 billion gallons (136 Gl) of biofuels by 2022, of which 21 billion (80 Gl) should come from non‐cornstarch feedstock (Gelfand et al ., ; Qin et al ., ). Switchgrass ( Panicum virgatum L.), a perennial grass native to the North American prairie, is sought as an alternative bioenergy source (Lee et al ., ; Sanderson & Adler, ).…”

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

“…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, ).…”

Yield and quality development comparison between miscanthus and switchgrass over a period of 10 years

“…However, criticism of the production of food and feed crops grown especially for energy purposes, such as maize or rapeseed, has motivated the search for high-yielding non-food energy crops. In recent years, the establishment of perennial crops has emerged as a very viable option mainly due to their comparative ecological advantages over annual energy crops [27,28,32]. Among these, the C4 grasses miscanthus and switchgrass combine the potential to deliver high biomass yield and ability to grow under a wide range of climatic conditions [21].…”