“There has been growing interest in the utilization of rice hulls as a biomass fuel. The resource is abundant in all large rice producing countries, but its efficient use requires the development of high tech combustion facilities.”
Biopact reports on growing interest in the conversion of agricultural waste from rice farming into useful energy. After rice is harvested from the paddy and processed, there is a large amount of biomass waste. Ajinomoto will purchase rice hulls from farmers in the surrounding area, where large quantities of the hulls go unused. This will mark the first time, at an overseas production site, that the company has made use of biomass as a fuel.
According to the IEA’s Bioenergy Task 33 on thermal biomass gasification, the leftover rice husks have a relatively high energy content (18 GJ/ton – higher heating value). Roughly 280kg of hulls remain after the rice is processed, thus, each ton of processed rice could represent around 120 kWh of energy from waste.
By the end of 2008, Japan’s Ajinomoto Co., a global food processor, will switch from oil to rice hulls for most of the fuel consumed at one of its key seasonings plants in northern Thailand. The biomass resource is abundantly present in the region, but has no market value. Farmers and rice processors often simply burn the hulls as waste, which releases carbon dioxide into the atmosphere. Ajinomoto now wants to utilize the biomass in an efficient combustion system to power a large food plant and so cut back its own emissions.
The Fraunhofer Institute – Europe’s leading applied technology institute – is developing a highly efficient circulating fluidized bed combustion system that unlocks the energy potential contained in biomass residues.
Construction of such a system requires significant capital investment since the feedstock is subjected to high temperatures in the absence of oxygen levels, and a pressurized environment must be maintained. Ajinomoto is applying for the project to be registered as a CDM (Clean Development Mechanism) by the UN. In addition to UN certification, Ajinomoto is preparing to apply to the governments of Japan and Thailand to receive credit for emissions reduction.
Proponents of such biomass gasification argue that there is a net reduction in greenhouse gases due to the amount of fossil fuel not being mined, transported and burned to generate electricity for operation of the food plant in Thailand. Since core operation of the food plant is fermentation of sugars and starches extracted from sugar cane and cassava to produce seasonings, Ajinomoto wants to build a combined heat and power system similar to a project underway in Brazil. In addition to the biomass-fueled, steam-generated electric power plant, heat from the conversion will be utilized in the fermentation process.
As the biomass fuel adds no carbon dioxide emissions the atmosphere because the CO2 released during the combustion process is absorbed by plants as they grow, Ajinomoto’s carbon footprint will improve considerably by utilizing this ‘carbon neutral’ form of energy. The switch to rice hulls will reduce annual CO2 emissions by around 100,000 tons, or nearly 5 per cent of the global group’s annual total.
Heating with biomass results in a carbon neutral cycle. “Major energy companies, including France’s nuclear giant AREVA (more here) and the Thai Board of Investment (here), are building biomass power plants in Thailand with dedicated technologies for rice husks.”
Biopact includes residue-to-product ratios in a convincing argument for making use of the energy potential in this biomass residue. The residue-to-product ratio for rice husks is between 0.20 to 0.35. For each ton of rice produced, some 200 to 350 kilograms of husks are left over; the average is 280 kg/ton.
The caloric value of rice husks is between 13 to 19 MJ/kilogram; the average is closer to the higher heating value of 18MJ/kg.
Now consider that Thailand as a whole produced some 29.4 million tons of rice in 2004… If all rice hulls were used in gasification or combustion systems with an overall efficiency of 33 per cent, the country’s technical energy potential from rice husks alone can be estimated be around 49.5 TJ of energy.
Engineer-Poet included rice straw as one type of feedstock to be used in his waste-to-energy approach, which starts with carbonizing the biomass. His approach differs in that he advocates running the gas produced — carbon monoxide, carbon dioxide, traces of methane, etc. plus hydrogen and water vapor — into a solid oxide fuel cell. He also advocates the use of algae capture of carbon emissions in the exhaust from the fuel cell.
APEC (Asia-Pacific Economic Consortium) “Expert Consultation on Biofuels” recommends that countries such as Thailand and Vietnam consider thermoelectric power plants as a means of making better use of crop residues, especially rice and wheat straw, which are largely being burned in most Asian countries.
The APEC experts were more cautious about BTL (Biomass-To-Liquids). The Biopact post noted that rice also yields a large amount of straw, which is being investigated as a feedstock in the production of cellulosic ethanol. Cellulosic ethanol could be “game changing“, since it demonstrates a better EROEI, and can have a better emissions profile, depending upon how it is made.
Still it is important to consider how to “close the loops”. Rapid heating of biomass in the absence of oxygen results in vaporization of the feedstock. The resulting gases pass into a cyclone where solid particles—char—are extracted. Just as the rice farmers burned the rice straw, the agri-char could be used as “a form of slow release fertilizer”. Not only does it enhance the soil enhancer, such charcoal burial is a means of carbon sequestration.
References:
Nikkei (via TradingMarkets): Japan’s Ajinomoto to use rice hulls to fuel Thai plant – October 30, 2007
Biopact: French nuclear energy giant AREVA to build 6 biomass power plants in Thailand and Brazil – March 13, 2007
Biopact: Unlocking the vast energy potential of rice husks – August 15, 2006
Biopact: Surin, Thailand: first biomass power plant using rice husks starts feeding electricity to grid
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Mike Millikin relays a warning from Oxfam International about the European Commission’s target of a 10% biofuel composition in member states’ transport fuels by 2020.
In a report, entitled “Biofueling Poverty“, that details why the EU renewable fuel target may be disastrous for poor people, the authors express concern about an agro-industrial model they see emerging.
In 1984 York Shipley received a U.S. Patent (#370248) for a fast fluidized bed reactor.
The waste-to-energy approach involving carbonization, as advocated by Engineer-Poet, is similar to what is described in Wikipedia as Advanced (Circulating), Pressurized, Fluidized Bed Combustion. The process described therein is combined cycle, i.e., uses gas turbine and steam turbine for electric power generation.
Instead, EP suggests burning the fuel gas from the carbonizer in a solid oxide fuel cell. According to EP, replacing the gas turbine with a fuel cell improves the efficiency of the process.
Also, the feedstock for such a process typically has been pulverized coal, whereas the approach suggested in the post and references make use of biomass instead.
Biopact has a post stressing the chances for poverty alleviation afforded by biofuels.
The Biopact post is a redux, perhaps prompted by the Oxfam postion statement, where they took issue with assertions by Jean Ziegler.
Nevertheless, biopact contends that “many poor countries [particularly in Africa] have a very large potential to produce sustainable biofuels that do not impact food security negatively.”
There are qualifiers with such endorsement. The FAO, the UNCTAD, the UNIDO, as well as the WorldWatch Institute, have said for biofuels to help end global hunger “will require a major overhaul of trade rules, an active effort to engage small farmers and poor rural communities in the sector, and a rethink of the massive biofuel subsidies paid to wealthy farmers in the EU and the US.”
The Temas Blog Energy Reading List includes a CEPAL/FAO report in Spanish and English about “Opportunities and Risks Arising from the Use of Bioenergy for Food Security in Latin America.” The Temas Blog also has a recent post about a UN Economic Commission for Latin America and the Caribbean (ECLAC/CEPAL) recently released report that evaluates the prospects for biodiesel development in Central America generally, and individually in Costa Rica, El Salvador, Guatemala and Honduras, and basically discourages biodiesel development for these countries.
Dr Alastair Martin is leading a project at the University of Mancester to integrate a fluid bed gasifier with a small scale gas turbine.
According to the university press release, Doc Martin and his team “envisage that excess electricity will be exported to the grid as ‘green energy’ – converting what is currently an environmental liability into a substantial income stream.”
While focussing on the development of small systems, it is unknown whether the team refers to them as “chickenshit operations“.
Picture: rice is Bangladesh’s first crop, yielding an abundant stream of residues, such as the rice husks transported in this barge, that can be efficiently used in modern bioenergy systems.
The Biopact team reports:
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