Lignocellulosic‐based bioenergy and water quality parameters: a review

Abstract

High rates of crop residue removal as biofuel feedstocks could increase losses of nonpoint source pollutants, negatively affecting water quality. An alternative to residue removal can be growing dedicated bioenergy crops such as warm season grasses (WSGs) and short‐rotation woody crops (SRWCs). Yet, our understanding of the implications of growing dedicated bioenergy crops on water quality is limited. Thus, we (i) synthesized and compared the impacts of crop residue removal, WSGs, and SRWCs on water quality parameters (i.e., sediment and nutrient runoff, and nutrient leaching) and (ii) identified research gaps for growing dedicated energy crops. Literature indicates that residue removal at rates >50% (residue retention up to 4.71 Mg ha−1) can increase runoff by 5–15 mm, sediment loss by 0.2–7 Mg ha−1, NO3–N by 0.58–1 kg ha−1, and sediment‐associated C by 0.3–57 kg ha−1 per rainstorm event compared to no residue removal. Crop residue removal may also increase nutrient leaching. Studies on the impacts of growing WSGs as dedicated bioenergy crops at field scale on water quality parameters are few. However, WSGs when used as conservation buffers reduce losses of sediment by 66–97%, nutrients by 21–94%, and contaminants by 9–98%. This suggests that if WSGs were grown as dedicated bioenergy crops at larger scales, they could reduce losses of nonpoint source pollutants. Literature indicates that SRWCs can consistently reduce NO3–N leaching. More modeled than field data are available, warranting further field research on (i) field data collection from WSGs and SRWCs from marginal lands, (ii) growing monoculture or polyculture of WSGs, and (iii) large‐scale production of energy crops. Overall, dedicated bioenergy crops, particularly WSGs, can reduce losses of nonpoint source pollutants compared to residue removal and be an important strategy to improve water quality if grown at larger scales.

Marginal Lands to Grow Novel Bio-Based Crops: A Plant Breeding Perspective

“…This is especially true considering that several biomass perennials are drought tolerant (Mehmood et al, 2017), can be irrigated using wastewaters (Barbosa et al, 2015), and can suffice their water needs with seasonal rainfalls in temperate climates (Robertson et al, 2017). In addition, MPBCs improve water quality and water management, as their extensive roots, prolonged soil coverage, and positive effect on soil structure and porosity promote water penetration into soils (Blanco-Canqui, 2016;Fernando et al, 2018), minimizing water runoff and soil erosion (Blanco-Canqui, 2016;Acharya and Blanco-Canqui, 2018). Furthermore, the low leaching fluxes and little agrochemical needs of MPBCs minimize water pollution (Blanco-Canqui, 2016;Acharya and Blanco-Canqui, 2018).…”

“…In addition, MPBCs improve water quality and water management, as their extensive roots, prolonged soil coverage, and positive effect on soil structure and porosity promote water penetration into soils (Blanco-Canqui, 2016;Fernando et al, 2018), minimizing water runoff and soil erosion (Blanco-Canqui, 2016;Acharya and Blanco-Canqui, 2018). Furthermore, the low leaching fluxes and little agrochemical needs of MPBCs minimize water pollution (Blanco-Canqui, 2016;Acharya and Blanco-Canqui, 2018). Finally, several perennial crops (e.g., willow, giant reed, miscanthus) can sequester contaminants (e.g., Cd, Pb, Zn, Cu) and pollutants from soils and water (Bandarra, 2013;Boléo et al, 2015;Costa et al, 2016), being therefore good options to remediate contaminated MALs and depurate polluted water streams (Barbosa et al, 2015;Costa et al, 2016;Acharya and Blanco-Canqui, 2018).…”

“…Furthermore, the low leaching fluxes and little agrochemical needs of MPBCs minimize water pollution (Blanco-Canqui, 2016;Acharya and Blanco-Canqui, 2018). Finally, several perennial crops (e.g., willow, giant reed, miscanthus) can sequester contaminants (e.g., Cd, Pb, Zn, Cu) and pollutants from soils and water (Bandarra, 2013;Boléo et al, 2015;Costa et al, 2016), being therefore good options to remediate contaminated MALs and depurate polluted water streams (Barbosa et al, 2015;Costa et al, 2016;Acharya and Blanco-Canqui, 2018).…”

Soil carbon increased by twice the amount of biochar carbon applied after 6 years: Field evidence of negative priming

“…Corn residues are increasingly being removed for livestock feeding and bedding, and for biofuel production. High rates of corn residue removal can increase the risks of soil erosion and reduce soil C storage (Acharya & Blanco‐Canqui, ; Blanco‐Canqui, Stalker, et al, ; Blanco‐Canqui, Tatarko, Stalker, Shaver, & Van Donk, ; Laird & Chang, ; Ruis et al, ). Adding biochar to corn fields is a potential strategy to mitigate the negative effects of residue harvesting on soil quality and C stocks (Backer, Schwinghamer, Whalen, Seguin, & Smith, ; Laird & Chang, ; Ventura et al, ).…”

Soil N2O emissions as affected by long‐term residue removal and no‐till practices in continuous corn

“…Despite these potential benefits, the environmental consequences of residue removal to support cellulosic ethanol production remain poorly understood. Concerns have been raised about impacts on crop productivity (Johnson et al, ; Karlen & Johnson, ), soil organic carbon (SOC) stocks (Liska et al, ), water quality (Acharya & Blanco‐Canqui, ; Gramig, Reeling, Cibin, & Chaubey, ), and soil GHG emissions (Jin et al, ; Qin et al, ). An important criterion of the Renewable Fuel Standard is that cellulosic biofuel production must reduce GHG intensity by 60% compared to gasoline.…”