Potential bioenergy options in developing and developed countries and their possible impact:PART ONE

Bioenergy is physical energy extracted from biomass. It can be electricity produced from biomass, cooling or heating, biofuels such as biogas, bioethanol, biodiesel and so on. It is an environmentally friendly, cost-effective and locally available source of energy. Developing countries can be benefited from these resources in creating income and labor opportunities, alleviating food security problems and poverty. In developed countries, bioenergy contributes a lot in reducing oil dependency and boosting their economy.

Agricultural energy crops

In the united sates, short rotation woody crops and herbaceous crops have attracted attention. Willow, eucalyptus is examples of short rotation crops while switch grass, energy cane and sorghum are examples of herbaceous crops. The ethanol business in the United States is based on corn starch.

Energy crops like straw can be combusted to produce heat or fermented to produce biogas. Biomass can be combusted in traditional Grate combustion or in more advantageous fluidized bed combustion technologies. Gasification of biomass and waste is another alternative to produce power and heat from biomass. The syngas produced is used to synthesize transportation fuels liquids like DME and methanol. Gasification can be carried out in small scale or large scale basis using fixed and fluidized beds. In biomass based integrated gasification combined cycle plants biomass can be used to produce heat and electricity. Biomass can also be heated directly in the absence of air to produce liquid fuels in pyrolysis technology. It can be carried in a small and large scale basis. The bio-oils can be utilized for various energy requiring activities. Manure and farm biomass can also be used for biogas production. Heat and power can also be produced from these resources using steam cycle.

Barriers in the utilization of agricultural energy crops can be classified as technical and non technical. Small scale power production technologies have high power production costs. Theses plants use steam cycle which have low cycle efficiencies. Additionally, variations in rainfall and fuel price leads to fuel supply and fuel quality problems in heat and power production. Efficiency improvement and reduction of costs must be targets of research and development activities. NOE reports summarized, lack of knowledge in conversion to fuels and scale up of lignocelluloses crops production to be major technical barriers and unpredictable economic conditions and legislation and uncertain sustainability of lignocelluloses crops as major non technical barriers.

In large scale combined heat and power plants, slagging; fouling and corrosion are major technical problems. Co firing with fossil fuels can be one solution to avoid these problems. Non technical problems in this area are high investment cost requirement and competition form pulp and paper industries. Appropriate technologies for biomass combustion should be developed and technologies should also be improved. Additionally efficiency improvement and high power to heat ratio should be research goals.

Liquid Biofuels

Liquid transportation fluids are bioethanol from sugar and starch residues and biodiesel from vegetable oils. Ethanol can be produced by fermentation from sugars or after hydrolysis from starch or cellulose. Biodiesel is produced from rapeseed using trans-esterification reaction. Synthesis gas prom gasification can be converted in to liquid fuels using Fischer-Tropsch process. MTBE and ETBE can be produced from methanol using methanol and ethanol by fermentation and gasification. Hydrogen can also be produced from gasification of biomass.

Liquid fuels like ethanol can be blended up to 5% in existing cars and also it can be used completely up to 100% in ethanol cars. The blending of ethanol with gasoline leads to better engine performance. Hence, ethanol can play significant role in supply of energy for the transport sector. Similar to other biofuels, cost is a major barrier in utilization as a transport fuel.

Biodiesel can be used as a diesel fuel. Ethanol and biodiesel are solvents and hence incompatible with materials used in cars. Elastomers used in fuel supply system and paints can be dissolved. Biodiesel contains double carbon-carbon bonds which can cause polymerization.

Methanol could be potential transportation fuel is methanol powered fuel cells and fuel cell electric vehicles are developed. Methanol can be produced from biomass by gasification. The syngas thus produced is then synthesized in to methanol.

Hydrogen is an excellent fuel for transportation. It can be used as fuel for fuel cells. Gasification, water shift and fast pyrolysis are some of thermo chemical methods of production. If problems with distribution and storage are resolved, hydrogen is an excellent fuel for transport.

Lack of infrastructure for blending and distribution is barriers in implementation of biofuels in EU.Other barriers are high capital cost, high feed stock cost, availability feedstock and logistics of feedstock supply. Fuel standards are non technical barriers in utilization of biofuels. NOE report stated that, the European standard for unleaded petrol and for diesel limits blending of respectively bioethanol in gasoline and biodiesel in petroleum to 5%. It may not compete with petroleum products due to extensive use of energy in the farming process.

Second generation liquid biofuels are made from lignocelluloses biomass such as wood, straw and grass. This leads to lower cost as compared to first generation liquid biofuels like ethanol and smaller land requirement. Additionally land that is not suitable for agriculture can be used to produce biofuels reducing its impact on usage of suitable land.

Fischer-Tropsch diesel from syngas is low cost alternative; however technology for this option, like second generation biofuels, needs development. Product diversification like co production of high value products can help reduce costs further.

Production of ethanol form lignocellulosic biomass involves pretreatment, hydrolysis and ethanol recovery. Using enzymatic or acid hydrolysis fermentable sugars are generated and they are converted to ethanol by microbial action. Major bottleneck for biomass to ethanol conversion is the cost of cellulose enzymes. It was also stated that solid state fermentation provides the ability to use agro-industrial and biomass as raw materials. It requires lesser skilled man power and infrastructure.

Waste to energy

Municipal solid waste can be fermented to produce biogas. Incineration is another option to produce heat. Wastes can also serve as feed for gasification, combustion and pyrolysis technologies. Mixed MSW has an average carbon content of 25 %. The production of biomass residues such as food by products, fiber and forest production exceeds 111EJ/year.

Cost like other bioenergy options is a major barrier. Additionally environmental concern is a key issue as energy conversion processes has to balance inertisation of waste streams, maximizing energy generation and restricting emissions. It was stated that some residues can not be used because of collection and transport would be prohibitive and agronomic conditions require recycling to the land.

Waste to energy conversion is technically constrained due to poor homogeneity of mixed waste hence waste incineration requires special waste fraction or sorting .While supply is not barrier; calorific value of the waste varies by season and region, making the design difficult. Lack of public acceptance is a non technical barrier and can be improved through public information on environmental data of plants in their regions.

To be continued.....