Bio-Energy and Biochar

 

This research explores the opportunities and constraints to combining a biochar soil management with energy production using novel low-temperature pyrolysis. Three real-world issues justify this approach: (1) The ever increasing pressure on rural land users to generate sufficient income from their land with decreasing market prices for food; (2) the necessity to provide sustainable production systems that minimize on- and off-site pollution and soil degradation; and (3) the demand for solutions to global warming.

While food prices do not increase sufficiently enough to ensure healthy farm economies without subsidies in many industrialized countries, energy prices increase at unprecedented rates. Within the past two years, gas and diesel prices increased by 150% (DOE, 2005). In contrast, the proportion of a household income spent for food decreased from 21% in 1950 to 10% in 2000 (ERS, 2005). One strategy to resolve this dilemma for farmers is to engage in energy production over the long term in addition to food production in order to diversify income. Several different strategies for land-based bio-energy production exist that build on modern biomass technology (in contrast to traditional biomass, UNDP 2004). The underlying principle is usually the sustainable land-based production of an energy crop or the use of waste biomass (also animal manures!) and the conversion into bio-fuels by various mechanisms. Possible avenues for producing bio-fuels from biomass are ethanol production through microbial fermentation, extraction of oils from crops, pyrolysis and gasification of biomass (Caputo et al., 2005). Farmers have begun to understand the economic opportunities associated with bio-energy. This proposal introduces an emergent strategy of combining energy production using modern biomass with land application of bio-char which is a residue from the energy production that has multiple environmental benefits.

The proposed technology is low-temperature pyrolysis that yields bio-oil, hydrogen or directly electricity as the energy carrier (including valuable co-products), with bio-oil being the more advanced and more wide-spread technology (Meier and Faix 1999; Bridgwater et al. 2002). The biomass feedstock may include a wide variety of biomass (Yaman 2004) such as wood chips or pellets, bark, crop residues such as nut shells or rice husks, and grass residues such as bagasse from the sugarcane industry. More importantly, however, planted energy crops can be used with the sole purpose of producing bio-fuels, such as short-rotation woody plants (e.g. willow), grasses (e.g. Miscanthus spp.), or herbaceous plants. The key for securing environmental benefits is the production of a biochar by-product during pyrolysis which can be applied to soil.

Reading:
Day, D., Evans, R.J., Lee, J.W. and Reicosky, D.: 2005, ‘Economical CO2 , SOx , and NOx capture from fossil-fuel utilization with combined renewable hydrogen production and large-scale carbon sequestration', Energy 30 , 2558-2579.
Lehmann J 2007 Bio-energy in the black. Frontiers in Ecology and the Environment 5, 381-387.
Lehmann, J., Gaunt, J. and Rondon, M.: 2006, 'Bio-char sequestration in terrestrial ecosystems – a review', Mitigation and Adaptation Strategies for Global Change 11, 403-427
Li, X., Hagaman, E., Tsouris, C. and Lee, J.W.: 2003, ‘Removal of carbon dioxide from flue gas by ammonia carbonization in the gas phase', Energy & Fuels 17 , 69-74.
Yaman, S.: 2004, ‘Pyrolysis of biomass to produce fuels and chemical feedstocks', Energy Conversion and Management 45 , 651-671.

News Feature article in NATURE:
Marris, E. 2006 'Black is the new green', Nature 442: 624-626.
Lehmann, J.: 2007, 'A handful of carbon',Nature 447, 143-144.
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