USDA researchers test biomass pyrolisis plant for the production of bio-oil
Overcoming logistical challenges
A major motivation for the research is to overcome some of the logistical challenges associated with biomass fuels. The challenge of using ligno-cellulosic energy crops is to overcome their low density. Bales of for example switchgrass are light and very bulky and require too much space on trucks or rail to make transportation to a central processing facility economically feasible. The idea is to transform them into bio-oil on-site, near the plantation, after which the energy rich, high density liquid can be transported more efficiently to central refineries.
Other challenges are difficulties associated with breaking down the complex carbohydrates in switchgrass to make simple sugars that can be converted into ethanol through the process of fermentation. These difficulties result in the current estimate that ethanol from switchgrass costs about twice as much as ethanol from grain crops, such as corn.
But according to the ARS researchers, pyrolysis offers a way to overcome both problems at once. By heating the biomass in an absence of oxygen - called pyrolysis - the green feedstock is broken down efficiently into a liquid that can be easily transshipped to central refineries and upgraded to fuels and chemicals.
In order to test the concept, they built a unique pilot-scale reactor that uses a hot sand medium (called a fluidized-bed reactor) to convert perennial grasses to bio-oil and have now tested the reactor on switchgrass. They obtained the following results:
- The reactor was able to use switchgrass as a feedstock and produce a quantity of bio-oil that was 60% of the weight of the switchgrass fed into the reactor.
- They analysed the composition and fuel properties of the produced liquid and found that the energy content was about the same as the parent switchgrass but the density was more than 2.5 times greater.
- The results show that char yielded would suffice in providing all the energy required for the endothermic pyrolysis reaction process.
- The tests showed over-all energy conversion efficiencies ranging from 52 to 81%.
Decentralised production
In the larger order of things, the technology is exceptionally suited for the developing world, where biomass productivity potentials are high, but where infrastructures are underdeveloped. In principle, the technology allows for decentralised 'crude oil' production by small producers, who sell to refineries (earlier post).
The ARS researchers hint at this concept:
bioenergy :: biofuels :: energy :: sustainability :: energy crops :: biomass :: lignocellulosic ::fast pyrolisis :: biomass-to-liquids :: bio-oil :: decentralisation ::
the study provides useful information for companies interested in building small scale distributed pyrolysers that could be used by farmers "on the farm" to produce a pyrolytic oil. Farmers could then sell the product as a "crude oil" to oil refiners, who in turn, would convert it into transportation or heating fuels. If successful, this would lead to increased opportunities for farmers who could put marginal lands into [tropical grass] production and help drive a renewable fuels economy in rural [areas].The study includes mass and energy balances of this system, yielding useful parameters for future economic and design studies.
More information:
Boateng, A.A., Daugaard, D.E., Goldberg, N.M., Hicks, K.B. 2007. Bench-scale fluidized-bed pyrolysis of switchgrass for bio oil production. Industrial and Engineering Chemistry Research 46, p.1891-1897.
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Saturday, April 07, 2007
The global biofuels revolution: challenges, options, recommendations
The report was recently presented and discussed at a conference, where both the IDB and the Interamerican Ethanol Commission convened. The following videos highlight contributions of two speakers: Roberto Rodrigues (former Brazilian minister of agriculture) and David Rothkopf who prepared the study.
Rothkopf discusses the confluence of major factors that make the case for biofuels: instable and insecure oil markets, the evidence for climate change and the need for low carbon fuels, the biotech revolution, and rapid growth in the developing world. Green fuels offer opportunities to create an entirely new energy paradigm that confronts this situation. Key words are decentralisation, fuel diversification, sustainability and social inclusion.
However, many challenges remain, such as the need to develop new technologies, investments in infrastructures and the creation of global and regional biofuel policies and markets. The speaker further focuses on current trends and the potential of Latin America.
Roberto Rodrigues, current co-chair of the Interamerican Ethanol Commission, former agriculture minister under Brazilian president Lula's first government, and professor of 'world economics' at the University of São Paulo. Rodrigues explains why the big issue for 20th century agriculture was achieving global food security, and why for the 21st century it will be energy security. The professor sees a radical change in the geography of energy and agriculture, with the Global South taking advantage of its vast bioenergy potential to leapfrog into a green development era. Rodrigues continues by focusing on the food versus fuel issue as it relates to Brazil. He concludes with a discussion of technological progress in the sector.
More information:
IDB: "IDB targets $3 billion in Private Sector Biofuel Projects" - April 2, 2007.
IDB presentation of the study "A Blueprint for Green Energy in the Americas - Strategic Analysis of Opportunities for Brazil and the Hemisphere", April 2007.
Video fragment credits: IDB, C-Span [entry ends here]
bioenergy :: biofuels :: energy :: sustainability :: ethanol :: biodiesel :: biomass :: energy security :: climate change :: rural development :: Brazil :: Latin America :: Africa ::
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