Bioenergy crop productivity and potential climate change mitigation from marginal lands in the United States: An ecosystem modeling perspective

Abstract

Growing biomass feedstocks from marginal lands is becoming an increasingly attractive choice for producing biofuel as an alternative energy to fossil fuels. Here, we used a biogeochemical model at ecosystem scale to estimate crop productivity and greenhouse gas (GHG) emissions from bioenergy crops grown on marginal lands in the United States. Two broadly tested cellulosic crops, switchgrass, and Miscanthus, were assumed to be grown on the abandoned land and mixed crop-vegetation land with marginal productivity. Production of biomass and biofuel as well as net carbon exchange and nitrous oxide emissions were estimated in a spatially explicit manner. We found that, cellulosic crops, especially Miscanthus could produce a considerable amount of biomass, and the effective ethanol yield is high on these marginal lands. For every hectare of marginal land, switchgrass and Miscanthus could produce 1.0-2.3 kl and 2.9-6.9 kl ethanol, respectively, depending on nitrogen fertilization rate and biofuel conversion efficiency. Nationally, both crop systems act as net GHG sources. Switchgrass has high global warming intensity (100-390 g CO 2 eq l À1 ethanol), in terms of GHG emissions per unit ethanol produced.Miscanthus, however, emits only 21-36 g CO 2 eq to produce every liter of ethanol. To reach the mandated cellulosic ethanol target in the United States, growing Miscanthus on the marginal lands could potentially save land and reduce GHG emissions in comparison to growing switchgrass. However, the ecosystem modeling is still limited by data availability and model deficiencies, further efforts should be made to classify crop-specific marginal land availability, improve model structure, and better integrate ecosystem modeling into life cycle assessment.

A nutrient-based sustainability assessment of purpose-grown poplar and switchgrass biomass production systems established on marginal lands in Canada

“…This yield range is consistent with poplar biomass yield reported in many studies (Aylott et al 2008;Dillen et al 2013;Marsal et al 2016). Similarly, switchgrass harvestable biomass yield (stem and leaves) ranged from 1.6 t ha −1 (SGN) to 2.6 t ha −1 (SGC), which can be compared with the average yield of 3.5 t ha −1 yr −1 reported in other studies on marginal lands (Qin et al 2015;Marsal et al 2016). However, relatively lower SGC yields in this study can be attributed mainly to the following establishment issues at the Kemptville site: crop failure due to early frost during the establishment year (2014) and uncontrolled weeds during subsequent years.…”

“…Studies suggest that nutrient requirements of purpose-grown biomass crops are relatively less and, hence, these crops can be successfully grown on marginal lands (Schmer et al 2005). Although growing biomass crops on marginal lands is supported for many reasons such as it avoids conflict with food crop production and carbon emission from land use change and land reclamation (Tilman et al 2009;Dillen et al 2013), the key focus is on biomass production for biofuels and bioproducts (Qin et al 2015). In Canada, herbaceous biomass crops are generally harvested once a year, whereas woody crops are harvested over a short rotation of 3-4 yr (Hangs et al 2014b).…”

“…From a nutrient perspective, even though biomass crop productivity is mainly driven by the availability of N, P, and K (Brown and Driessche 2005;Parrish and Fike 2005;Guillemette and DesRochers 2008), the role of N alone has been emphasised in several studies (McLaughlin and Kszos 2005;Rennenberg et al 2010;Qin et al 2015). This nutrient cycling aspect is poorly understood for purposegrown poplar (Populus spp.)…”

Growing Dedicated Energy Crops on Marginal Lands and Ecosystem Services

“…The research needs for the production of biofuel feedstocks on marginal lands include: (Qin et al, 2015). At present, the limited experimental data availability limits the ability of models to accurately estimate biomass production potential for different marginal lands at regional and global scales.…”

“…These modeling studies have suggested that marginal lands offer a large potential for producing dedicated bioenergy crops while sequestering soil C, reducing net greenhouse gas emissions, and improving water quality (Davis et al, 2010;Gelfand et al, 2011;Lee et al, 2012;Bandaru et al, 2013;Feng et al, 2015;Qin et al, 2015). However, few studies have synthesized field data to discuss the biomass yields and soil and environmental benefits from growing dedicated energy crops on different types of marginal lands.…”