Bio-fuels recommendations

Rapid advances in biofuel technology will create a dynamic market. Projected further increases in biofuel production over the coming decades involve the greater use of potentially lower cost biomass (lignocellulosics) as feedstock. Achieving this will require significant technological breakthroughs (pre-treatment, enzymes, recombinant microorganisms), while opening up the opportunity for the use of agricultural and forestry residues, new high biomass yielding energy crops and associated higher value fermentation products.

 Global bioethanol production is increasing rapidly. Bioethanol, conventionally produced from cane molasses by yeast fermentation, can also be produced from various agroindustial residues and plant wastes. Efficient process optimization and integration by combining production and recovery processes may lead to economic production of bioethanol. Projections by the US Department of Energy are that by 2020, the volume of ethanol produced from the conversion of lignocellulosic materials (biomass) will be twice that produced from corn. To achieve this goal, a number of technological obstacles should be overcome:

1. Development of cost effective pre-treatment strategies for the various lignocellulosic

materials,

3. Availability of robust recombinant microbes (yeasts, bacteria) for high ethanol yields

from the C5 (xylose, arabinose) and C6 (glucose) sugars from lignocellulosic hydrolysates,

4. Product and market development for the non-reactive lignin by-product

(approximately 15%) with potential for its use in paints and adhesives.

Brazil has played a leading role and it continues to be a global leader-although ethanol production from corn in the USA is now approaching Brazilian levels. A major difference between Brazil and the USA is that the industry cost structure and the use of sugarcane in Brazil as raw material (instead of corn) result in most advantageous cost. In Brazil, half of the current sugar crop is converted to fuel ethanol. The USA Department of Energy has announced major financial support for producing ethanol from lignocellulosics. Much more R&D input needs to be supported in Australia for second-generation processes for biomass to ethanol conversion, including the use of flexible pre-treatment plant design to facilitate use of a range of lignocullulosic raw material from both energy crops and agricultural forestry residues.

 Biodiesel, on the other hand, is generally produced from vegetable oils. Agroindustiral residues are still not used as a substrate for biodiesel, though the residual oil present in oil cake, a waste product of oil extraction units, holds great potential. In future, suitable residues with high lipid content may be used as potential raw materials for biodiesel production. Biotechnological procedures to produce biofuels from agroindustrial wastes and residues may be effective in reducing the emission of toxic pollutants and greenhouse gases, and in partly solving the worldwide fuel crisis.

 Biogas originates from bacteria during the process of biodegradation of organic materials under anaerobic conditions. All homogenous and liquid organic materials can be fermented or digested (e.g. faeces and urine from cattle, pigs and possibly poultry and wastewater from toilets). Waste and wastewater from food processing industries are suitable if they are homogenous and in liquid forms. Biogas is mainly composed of: 40-70% methane, 30-60% carbon dioxide, 1-5% other gases (0-1% hydrogen, 0-3% hydrogen sulfide). The biogas produced by a digester can be used in the same way as any other combustible gas and it yields a range of benefits for users, which are in general, the production of energy (heat, light, electricity), the transformation of organic wastes into high-quality fertilizer, the improvement of hygienic conditions through reduction of pathogens, etc., the reduction of workload, mainly for women, the positive environmental impact through protection of soil, water, air and woody vegetation and the economic benefits through energy and fertilizer substitution.

A barrier to the large-scale introduction of biogas technology is the fact that the poorer strata of rural populations often cannot afford the initial investment cost for a biogas plant. Financial support from the government can be seen as an investment to hold future costs due to the importation of petrol products and inorganic fertilizers, increasing costs for health and hygiene, as well as natural resource degradation. China is one of the leading countries in biogas construction in rural areas.

The development of biogas technology depends on the political will. It is the task of the government and administrative authorities to provide access to the technology and to secure and organize the requisite materials, financial resources and legal basis. Governments can play a supportive role in biogas research, information dissemination and the regulations for funding, subsidies or tax waiving.

In more general terms, it is essential to develop high performance microbes that are capable of producing biofuels with very high efficiency in order to compete with the fossil fuel. The strategies for developing microbial strains by systems metabolic engineering, which can be considered as metabolic engineering integrated with systems biology and synthetic biology, have been developed. Systems metabolic engineering allows successful development of microbes that are capable of producing several different biofuels including bioethanol, biobutanol, alkane, biodiesel an even hydrogen. Some examples of systems metabolic engineering approaches are strain development of Saccharomyces

cerevisiae, Escherichia coli, Zymomonas mobilis for ethanol production, Clostridium acetobutylicum, C. beijerinckii and E. coli for butanol and isobutanol production.

In order to develop economical and sustainable processes for biofuel production, the metabolic pathways of biofuel producers need to be optimally redesigned to achieve improved product yields, higher product concentration and productivity and product tolerance. Also, the whole process should be operationally inexpensive. It is expected that this combined strategy will result in the development of microorganisms capable of producing various biofuels cost effectively on industrial scale (Jang et

al., 2012; Liu et al. 2012).