Monday, April 09, 2012

An Early Conception of a Biomass to Liquids Economy

Given a sufficiently large production scale, liquid fuels such as diesel produced from crop residue could be economically competitive with petroleum-derived fuels at current price levels, suggests a new study by a team from the Stevens Institute of Technology. Their analysis is published in the ACS journal Energy & Fuels. _GCC

A recently published study in ACS Energy & Fuels claims that a particular conception for biomass to liquid fuel (Fischer Tropsch diesel BTL) can compete with petroleum diesel today. The overall BTL system involves collection of baled biomass at a local pyrolysis plant, where the solid biomass is converted to a much more energy-dense liquid pyrolysis product. The pyrolysis product is more economical to ship to central biorefinery plants which transform the pyrolysis product into diesel using gasification and Fischer Tropsch catalytic synthesis.
James Manganaro and Adeniyi Lawal performed a preliminary analysis of an integrated “Biorefinery Collective” biomass-to-liquids process based on distributed fast pyrolysis and centralized autothermal reforming (ATR) followed by Fischer-Tropsch synthesis. Assessing plant sizes of 2,000, 10,000, and 35,000 dry tonnes per day of biomass at 8% return on capital, they found required sales prices (exclusive of tax) of $3.30, $2.40, and $2.06 per gallon, respectively. The process comprises:

harvesting surplus biomass such as crop residue;

locally pyrolyzing the biomass into pyrolysis oil (PO), char, and noncondensable gas (NCG);

transporting the produced PO to a remote central processing facility;

converting the PO at this facility by autothermal reforming (ATR) into synthesis gas (CO and H2), followed by, at the same facility,

Fischer−Tropsch (FT) synthesis of the syngas into diesel fuel. _GCC
This is not a novel concept. But this approach is still in the early stages of development, in terms of becoming economically competitive.

Low natural gas prices help to make the process more competitive in one sense -- as a cheap industrial heat source. But cheap natural gas is a natural competitor feedstock against biomass, for F-T synthesis of diesel. Inexpensive high quality heat from high temperature gas-cooled modular nuclear reactors makes more sense as an industrial heat source for both BTL and GTL, than natural gas which is better used as a feedstock.

In other bio-energy news, Proterro has bioengineered a promising strain of cyanobacteria which is capable of cheap, high-yield production of very pure sucrose from CO2 and light. The company claims to be able to produce 10 X more sucrose per acre using bioreactors than is achievable from sugar cane production of sucrose.

CO2 isn't cheap in pure reagent form, of course. For Proterro to deliver on its claim of pure sucrose at less than $0.10 per pound, it must guarantee a cheap and reliable source of pure CO2. Cheap sugars will change the economic calculus of fermentable biofuels, once they become available in large quantities.

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