Annie F.A. Chimphango

Next-generation cellulosic ethanol technologies and their contribution to a sustainable Africa

The world is currently heavily dependent on oil, especially in the transport sector. However, rising oil prices, concern about environmental impact and supply instability are among the factors that have led to greater interest in renewable fuel and green chemistry alternatives. Lignocellulose is the only foreseeable renewable feedstock for sustainable production of transport fuels. The main technological impediment to more widespread utilization of lignocellulose for production of fuels and chemicals in the past has been the lack of low-cost technologies to overcome the recalcitrance of its structure. Both biological and thermochemical second-generation conversion technologies are currently coming online for the commercial production of cellulosic ethanol concomitantly with heat and electricity production. The latest advances in biological conversion of lignocellulosics to ethanol with a focus on consolidated bioprocessing are highlighted. Furthermore, integration of cellulosic ethanol production into existing bio-based industries also using thermochemical processes to optimize energy balances is discussed. Biofuels have played a pivotal yet suboptimal role in supplementing Africas energy requirements in the past. Capitalizing on sub-Saharan Africas total biomass potential and using second-generation technologies merit a fresh look at the potential role of bioethanol production towards developing a sustainable Africa while addressing food security, human needs and local wealth creation.

A global conversation about energy from biomass: the continental conventions of the global sustainable bioenergy project

The global sustainable bioenergy (GSB) project was formed in 2009 with the goal of providing guidance with respect to the feasibility and desirability of sustainable, bioenergy-intensive futures. Stage 1 of this project held conventions with a largely common format on each of the worlds continents, was completed in 2010, and is described in this paper. Attended by over 400 persons, the five continental conventions featured presentations, breakout sessions, and drafting of resolutions that were unanimously passed by attendees. The resolutions highlight the potential of bioenergy to make a large energy supply contribution while honouring other priorities, acknowledge the breadth and complexity of bioenergy applications as well as the need to take a systemic approach, and attest to substantial intra- and inter-continental diversity with respect to needs, opportunities, constraints and current practice relevant to bioenergy. The following interim recommendations based on stage 1 GSB activities are offered: — Realize that it may be more productive, and also more correct, to view the seemingly divergent assessments of bioenergy as answers to two different questions rather than the same question. Viewed in this light, there is considerably more scope for reconciliation than might first be apparent, and it is possible to be informed rather than paralysed by divergent assessments. — Develop established and advanced bioenergy technologies such that each contributes to the others success. That is, support and deploy in the near-term meritorious, established technologies in ways that enhance rather than impede deployment of advanced technologies, and support and deploy advanced technologies in ways that expand rather than contract opportunities for early adopters and investors. — Be clear in formulating policies what mix of objectives are being targeted, measure the results of these policies against these objectives and beware of unintended consequences. — Undertake further exploration of land efficiency levers and visions for multiply-beneficial bioenergy deployment. This should be unconstrained by current practices, since we cannot hope to achieve a sustainable and a secure future by continuing the practices that have led to the unsustainable and insecure present. It should also be approached from a global perspective, based on the best science available, and consider the diverse realities, constraints, needs and opportunities extant in different regions of the world. The future trajectory of the GSB project is also briefly considered.

Bioenergy and African transformation

Among the world’s continents, Africa has the highest incidence of food insecurity and poverty and the highest rates of population growth. Yet Africa also has the most arable land, the lowest crop yields, and by far the most plentiful land resources relative to energy demand. It is thus of interest to examine the potential of expanded modern bioenergy production in Africa. Here we consider bioenergy as an enabler for development, and provide an overview of modern bioenergy technologies with a comment on application in an Africa context. Experience with bioenergy in Africa offers evidence of social benefits and also some important lessons. In Brazil, social development, agricultural development and food security, and bioenergy development have been synergistic rather than antagonistic. Realizing similar success in African countries will require clear vision, good governance, and adaptation of technologies, knowledge, and business models to myriad local circumstances. Strategies for integrated production of food crops, livestock, and bioenergy are potentially attractive and offer an alternative to an agricultural model featuring specialized land use. If done thoughtfully, there is considerable evidence that food security and economic development in Africa can be addressed more effectively with modern bioenergy than without it. Modern bioenergy can be an agent of African transformation, with potential social benefits accruing to multiple sectors and extending well beyond energy supply per se. Potential negative impacts also cut across sectors. Thus, institutionally inclusive multi-sector legislative structures will be more effective at maximizing the social benefits of bioenergy compared to institutionally exclusive, single-sector structures.

Cationization of Eucalyptus grandis 4-O-methyl glucuronoxylan for application as a wet-end additive in a papermaking process

Abstract Hemicelluloses extracted prior to kraft pulping can subsequently be introduced as wet-end strength additives in a papermaking process. The 4-O-methyl glucuronoxylan (Me-GluX) extracted from Eucalyptus grandis (E. grandis) under mild alkaline conditions was cationized and added to bleached kraft pulp (BKP) from E. grandis before refining. The cationization by 2,3-epoxypropyltrimethylammonium chloride (ETA) was done in a central composite designed experiment. Me-GluX with an average molecular weight of 52,000 g mol-1 contained 27% Klason residue. The cationic Me-GluX had degrees of substitution of the cationic side chain between 0.05 and 0.73 and uronic acid content between 6.1% and 12.7%. The cationic Me-GluX as a wet-end strength additive was compared to cationic starch (CatStarch 134) in handsheets. The handsheets with cationic Me-GluX showed improvement in tensile, burst, and tear indices and had lower air permeability than those with CatStarch 134 at dosages between 1.0% and 2.0%. Accordingly, cationized Me-GluX is a potential green wet-end strength additive, which could fully or partially replace the synthetic and starch additives.

Effects of wheat-bran arabinoxylan as partial flour replacer on bread properties

Effects on physical properties of white bread of adding crude (E1) and partially purified (E2) arabinoxylans (AX) from wheat bran to partially replace flour during baking, were investigated to identify optimal dosage. The E1 and E2 had molecular weights of 620,000 and 470,000Da with arabinose to xylose ratio of 0.7 and 0.6, respectively. However, ferulic acid of 1.5mg/100g, was detectable only in E1. The AXs were added to 100g white bread formulae at dosages of 0.8-1.2% with flour removal of 2-3%(w/w). The dough increased water absorption by 2% in the specified dosage range. An optimum dosage of 0.8% with 2.5% flour removal maintained similar weight, volume, height and firmness as standard white bread. At this dosage, AX addition in white bread holds both increased health and economic benefits because of combined roles as soluble dietary fibre and flour replacer.

Single-step microwave-assisted hot water extraction of hemicelluloses from selected lignocellulosic materials – A biorefinery approach

The viability of single-step microwave-induced pressurized hot water conditions for co-production of xylan-based biopolymers and bioethanol from aspenwood sawdust and sugarcane trash was investigated. Extraction of hemicelluloses was conducted using microwave-assisted pressurized hot water system. The effects of temperature and time on extraction yield and enzymatic digestibility of resulting solids were determined. Temperatures between 170-200°C for aspenwood and 165-195°C for sugarcane trash; retention times between 8-22min for both feedstocks, were selected for optimization purpose. Maximum xylan extraction yields of 66 and 50%, and highest cellulose digestibilities of 78 and 74%, were attained for aspenwood and sugarcane trash respectively. Monomeric xylose yields for both feedstocks were below 7%, showing that the xylan extracts were predominantly in non-monomeric form. Thus, single-step microwave-assisted hot water method is viable biorefinery approach to extract xylan from lignocelluloses while rendering the solid residues sufficiently digestible for ethanol production.

Modifying solubility of polymeric xylan extracted from Eucalyptus grandis and sugarcane bagasse by suitable side chain removing enzymes

α-l-Arabinofuranosidase (AbfB) and novel α-d-glucuronidase (Agu1B) enzymes were applied for selective hydrolysis of beechwood (Fagus sylvatica) xylan (Sigma-Aldrich) as well as xylans extracted from Eucalyptus grandis and sugarcane (Saccharum officinarum L.) bagasse, leading to precipitation of these carbohydrate biopolymers. Hemicellulose extraction was performed with two mild-alkali methods, Höije and Pinto. Precipitation occurred after removal of 67, 40 and 16% 4-O-methyl-d-glucuronic acid (MeGlcA) present in polymeric xylans from beechwood, E. grandis (Pinto) and E. grandis (Höije), respectively. Precipitation was maximized at Agu1B levels of 3.79-7.53mg/gsubstrate and hemicellulose concentrations of 4.5-5.0% (w/v). Polymeric xylan from sugarcane bagasse precipitated after removal of 48 and 22% of arabinose and MeGlcA, respectively, at optimal AbfB and Agu1B dosages of 9.0U/g and 6.4mg/g, respectively. Both the purity of polymeric xylans and structure thereof had a critical impact on the propensity for precipitation, and morphology of the resulting precipitate. Nano-to micro-meter precipitates were produced, with potential for carbohydrate nanotechnology applications.

In situ enzyme aided adsorption of soluble xylan biopolymers onto cellulosic material

The functional properties of cellulose fibers can be modified by adsorption of xylan biopolymers. The adsorption is improved when the degree of biopolymers substitution with arabinose and 4-O-methyl-glucuronic acid (MeGlcA) side groups, is reduced. α-l-Arabinofuranosidase (AbfB) and α-d-glucuronidase (AguA) enzymes were applied for side group removal, to increase adsorption of xylan from sugarcane (Saccharum officinarum L) bagasse (BH), bamboo (Bambusa balcooa) (BM), Pinus patula (PP) and Eucalyptus grandis (EH) onto cotton lint. The AguA treatment increased the adsorption of all xylans by up to 334%, whereas, the AbfB increased the adsorption of the BM and PP by 31% and 44%, respectively. A combination of AguA and AbfB treatment increased the adsorption, but to a lesser extent than achieved with AguA treatment. This indicated that the removal of the glucuronic acid side groups provided the most significant increase in xylan adsorption to cellulose, in particular through enzymatic treatment.

A systems approach mapping of primary forest residues supply chain for sustainable production of bioenergy in Malawi

F the last few years, the production of butanol has been the focus of researchers’ attention when looking for alternatives to biofuels’ production. Interesting results have already been achieved with heterologous organisms such as Escherichia coli. However, native producers from clostridia group still presents the best alternative to succeed; as they possess all the machinery required and evolutionarily were optimized to produce butanol. However, there are several limitations that need to be assessed in order to control the production of other unwanted end-products such as ethanol, acetone, lactate or succinate that may deviate the fluxes away from butanol. Strategies of metabolic engineering have been on the table for over the last 15 years. However, the targets that seemed obvious at first, have proven not to increment significantly butanol titers showing that C. acetobutylicum metabolism is not as straightforward as it seemed. Going deep into understanding the solventogenic metabolism became therefore a key step into overcoming the difficulties to channel the metabolism towards butanol production. In this work, we apply deep in silico analysis in order to learn and understand the peculiarities of this microorganism metabolism. Our study suggests a new in silico strategy to maximize butanol production.

Postharvest technology for advancing sustainable bioenergy production for food processing

Purpose – Agricultural food residues (agro-residues) receive low economic returns and experience disposal problems. The food production and processing is often not configured to supply agro-residues for production of bioenergy needed in food processing. The feasibility of utilising agro-residues through advances in postharvest technology for sustainable bioenergy conversion is reviewed. The paper aims to discuss this issue. Design/methodology/approach – Agro-residues from maize, sugarcane and potatoes in five African countries were assessed from secondary data to identify suitable conversion technologies, energy products and configurations of bioenergy plants for applications in postharvest food processing. Findings – Strategic alignment of postharvest technology to bioenergy production systems is vital to advancing both food production and bioenergy that benefit rural communities in Africa. High economic returns are possible when the bioenergy plants are either annexure to existing agro-processing operat...