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Rapid And Effective Oxidative Pretreatment Of Woody Biomass At Mild Reaction Conditions And Low Oxidant Loadings
One route for producing cellulosic biofuels is by the fermentation of lignocellulose-derived sugars generated from a pretreatment that can be effectively coupled with an enzymatic hydrolysis of the plant cell wall. While woody biomass exhibits a number of positive agronomic and logistical attributes, these feedstocks are significantly more recalcitrant to chemical pretreatments than herbaceous feedstocks, requiring higher chemical and energy inputs to achieve high sugar yields from enzymatic hydrolysis. We previously discovered that alkaline hydrogen peroxide (AHP) pretreatment catalyzed by copper(II) 2,2 -bipyridine complexes significantly improves subsequent enzymatic glucose and xylose release from hybrid poplar heartwood and sapwood relative to uncatalyzed AHP pretreatment at modest reaction conditions (room temperature and atmospheric pressure). In the present work, the reaction conditions for this catalyzed AHP pretreatment were investigated in more detail with the aim of better characterizing the relationship between pretreatment conditions and subsequent enzymatic sugar release. Results: We found that for a wide range of pretreatment conditions, the catalyzed pretreatment resulted in significantly higher glucose and xylose enzymatic hydrolysis yields (as high as 80% for both glucose and xylose) relative to uncatalyzed pretreatment (up to 40% for glucose and 50% for xylose). We identified that the extent of improvement in glucan and xylan yield using this catalyzed pretreatment approach was a function of pretreatment conditions that included H2O2 loading on biomass, catalyst concentration, solids concentration, and pretreatment duration. Based on these results, several important improvements inpretreatment and hydrolysis conditions were identified that may have a positive economic impact for a process employing a catalyzed oxidative pretreatment. These improvements include identifying that: (1) substantially lower H2O2 loadings can be used that may result in up to a 50-65% decrease in H2O2 application (from 100 mg H2O2/g biomass to 35–50 mg/g) with only minor losses in glucose and xylose yield, (2) a 60% decrease in the catalyst concentration from 5.0 mM to 2.0 mM (corresponding to a catalyst loading of 25 mumol/g biomass to 10 mumol/g biomass) can be achieved without a subsequent loss in glucose yield, (3) an order of magnitude improvement in the time required for pretreatment (minutes versus hours or days) can be realized using the catalyzed pretreatment approach, and (4) enzyme dosage can be reduced to less than 30 mg protein / g glucan and potentially further with only minor losses in glucose and xylose yields. In addition, we established that the reaction rate is improved in both catalyzed and uncatalyzed AHP pretreatment by increased solids concentrations. Conclusions: This work explored the relationship between reaction conditions impacting a catalyzed oxidative pretreatment of woody biomass and identified that significant decreases in the H2O2, catalyst, and enzyme loading on the biomass as well as decreases in the pretreatment time could be realized with only minor losses in the subsequent sugar released enzymatically. Together these changes would have positive implications for the economics of a process based on this pretreatment approach. Author: Zhenglun LiCharles H ChenEric L HeggDavid B Hodge Credits/Source: Biotechnology for Biofuels 2013, 6:119 Continue reading
UK Government To Introduce Biomass Sustainability Criteria From April 2015
EBR Staff Writer Published 26 August 2013 UK government has asked the biomass industry to demonstrate fuel sustainability starting April 2015, failure of which may cost the financial aid allotted to the producers. The companies producing 1MW capacity or more using solid biomass or biogas feedstock are needed to demonstrate to claim support under the Renewables Obligation. In order to ensure sustainability of wood-fuel, the government stated that biomass electricity would produce over 70% greenhouse gas savings compared to fossil fuel alternatives. Minister of State for Energy and Climate Change Greg Barker said that the coalition is committed to delivering clean, affordable and secure energy for consumers and that includes an important role for biomass power as part of the UK’s energy mix. “The new criteria will provide the necessary investor certainty and, crucially, ensure that the biomass is delivered in a transparent and sustainable way,” added Barker. New criteria for sustainable forest management are formulated due to the issues including sustainable harvesting rates, biodiversity protection and land use rights for indigenous populations. Meanwhile, the Renewable Energy Association has welcomed the government’s sustainability criteria stating that it would ensure that only projects with strong ecological protections and high carbon savings can be supported under the Renewables Obligation (RO). REA chief executive Nina Skorupska said, “These sustainability criteria ensure that the UK can reap the benefits of biomass, safe in the knowledge that it is making a real dent in our carbon emissions and that ecologically sensitive land is being protected. Continue reading
UK Ignores Land Change In Biomass Criteria
By Dave Keating – 27.08.2013 draft proposalcirculated by the European Commission’s energy department earlier this month. The criteria would ensure that the extraction of energy from biomass, largely wood from forests, is not causing more emissions through land displacement than it abates. Under the UK proposal, published on Thursday (22 August), large biomass energy plants would have to demonstrate that they are emitting 66% less carbon than fossil fuel in order to qualify for renewable energy subsidies from 2014. This would rise to 72% in 2020 and 75% in 2025. The threshold is stricter than the 60% suggested by the Commission’s energy department. But like the energy department’s draft, the UK criteria would not factor in indirect land use change (ILUC), which would include such phenomena as loss of carbon storage potential for trees or the increased use of land for displaced food crops. The 2008 renewable energy directive obliged the Commission to come forward with sustainability criteria for biomass and biofuel, but these have been long delayed. A proposal put forward last year to factor ILUC into decisions about which biofuel can receive renewables subsidies and meet fuel objectives has encountered huge resistance from the biofuel industry, which says the restrictions would destroy their business. Environmental campaigners are angry that the draft proposal circulated within the Commission does not include ILUC, saying the Commission has backed off because it wants to avoid the same level of controversy it has encountered with the biofuel proposal. There is conflict with other Commission departments which want to include ILUC and carbon debt, according to Commission sources. However the biomass industry maintains that biomass does not cause ILUC in any significant way and comes from land that would not be used to grow food crops. The Commission is expected to put forward its proposal in October. © 2013 European Voice. All rights reserved. Continue reading
