Study finds biomass-to-liquids fuels could be economically competitive at current price levels; pyrolyzer and biorefinery collectives
|The biorefinery collective encompasses multiple pyrolyzer collectives. Credit: ACS, Manganaro and Lawal. Click to enlarge.|
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.
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.
|Block diagram of the process. Credit: ACS, Manganaro and Lawal. Click to enlarge.|
Manganaro and Lawal call the integrated enterprise of all the steps the “biorefinery collective” (BRC).
The higher density of pyrolysis oil compared to baled biomass reduces the transport cost to a central ATR plant; it also opens the possibility of pipeline transport, the authors note. They define a pyrolyzer collective (PC) as a collection of farms contained within a land area of arbitrary size in which each farm sends its crop residue to a single centrally located pyrolyzer within the land area where the biomass is converted to pyrolysis oil.
Just as the cost of crude oil has a heavy influence on current petroleum fuel prices, the cost of biomass is the largest single contributor to the final price of biomass-derived fuel and becomes more so as plant capacity increases, they found, leading to the need to improve methods of biomass gathering and delivery.
Other findings of their analysis include:
Char is a byproduct of the biomass process and when sold at $500/t contributes very measurably to the economics, reducing the price of diesel by $0.35/gal.
There appears to be on the order of a 12cent/gal benefit in using a 25 mi2 PC rather than a 14 mi2 PC due to the economy of scale of the pyrolyzer plant.
In order to make a measurable impact on reduction of fossil petroleum consumption in the US, one possible scenario calls for 10 BRCs producing 200,000 db each.
Future economic analyses, rather than taking a fixed price of biomass, should include accounting for the cost of (collecting) biomass as a function of the geographic land area as well as refinement of input data.
It must be borne in mind in comparing the economics of the nascent biomass to liquid fuel processes to the “mature”, century old, processes of crude oil or FT of natural gas or coal, that the biomass processes are on a learning curve and, over time, assuming commercial implementation, will more rapidly improve in economics relative to the mature processes. This also implies that early entrants into the field of biomass derived fuel would establish a competitive advantage. It then becomes a question of whether and when to enter the bio-derived fuel field in a committed way.
From this preliminary analysis, FT liquids derived from biomass, even without policy intervention, could be competitive at current prices at a sufficiently large production scale.—Manganaro and Lawal
James L. Manganaro and Adeniyi Lawal (2012) Economics of Thermochemical Conversion of Crop Residue to Liquid Transportation Fuel. Energy & Fuels doi: 10.1021/ef3001967