Biorefineries as sources of fuels and chemicals

Geoff Covey, Bruce Allender, Bronwyn Laycock and Mike O’Shea

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At present, the value of biofuels is such that only large biorefineries are likely to be economic except in special circumstances. Large biorefineries require a large capital investment and thus represent a large commercial risk. However, there are strategic reasons that make it desirable to some companies to enter the biofuel market now. Although the revenue from fuels from biorefineries is relatively low, some of the chemicals that form components of these fuels are of high inherent value. This paper shows that by extracting some chemicals from the products of fast pyrolysis and selling the remainder as fuel, even quite small biorefineries can become economically attractive.

INTRODUCTION

World annual energy demand in 2008 * was estimated to be  532 EJ/a and predicted to grow to 812 EJ/a by 2035 1 . Most  of the growth is in non  OECD countries, with an average  annual growth in demand being 2.3% vs 0.6% for OECD  countries.

The largest growth in absolute terms is predicted to be for  coal 1 . Renewables have the greatest percentage growth, but  this is from a very small base, and their absolute growth is  predicted  to  be  slightly  less  than  that  of  coal.  Most  of  the  growth  in  renewable  energy  is  expected  to  be  in  the  form  of hydro and wind power 1 .

Bio  liquids  are  predicted  to  rise  from  1.8%  by  volume  of  total liquid fuel consumption in 2008 to 4.2% in 2035. On  an  energy  basis  the  quantity  of  biofuels  is  much  less,  and  difficult  to  assess  because  of  the  wide  range  in  heats  of  combustion of different forms of these fuels.

Reserves  to  production  ratios  indicate  how  long  currently  known reserves of fossil fuels would last at current rates of  consumption.

1980 1995 2000 2007 2011
Oil 29 41.4 40.4 42.4 44
Natural Gas2 56.9 65.7 65 60.1 60.2
Coal 224 209 164 126

The reserves to production ratio of oil continues to rise gradually, and that for natural gas is falling slightly (i.e. the rate of discovery of new reserves is still similar to the rate of consumption) although some of this rise is due to known reserves which were previously regarded as uneconomic becoming economic because of rising prices.

The reserves to production ratio for coal is falling steadily, but this is partly because coal exploration is less vigorous, and known reserves are still very large.

Therefore in the short to medium term, scarcity is not the main driving force for the development of renewable energy; it is the desire to reduce carbon dioxide emissions.

As fossil fuels become more expensive (through scarcity and/or government charges) so renewable energy will become more competitive. Electricity can be generated by a number of means, but matching demand to supply from inherently variable and unpredictable sources such as wind and sunlight will be a major challenge. Steam raising for industrial facilities can be largely from biomass with little or no pre processing (though the quantities required will be massive).

Despite these possibilities, two problem areas remain – storage of electricity to match times of demand and generation, and liquid fuels for transport. The big issue will be liquid fuels for transport.

Railways can be electrified; there can be a return to some equivalent of trolley busses for urban public transport. Passenger cars and other light vehicles can be battery powered for urban use at least, or can be compressed air powered. However, it is difficult to see how foreseeable technology will enable ships, aircraft and heavy land vehicles to run on anything other than liquid fuels # , and it is here that biofuels must provide the solution.

Eventually fossil fuels must run out but this does not present an immediate incentive to do more than research – carbon taxes in various forms can improve the economics, but still make a very large plant something of a risk (e.g. if change of government leads to a reduction in carbon price)