“In order to acquire energy, it takes energy”
We talked about various sources and forms of energy over the past few months. We are so dependent on fossil fuels that the absence of this will have enormous economic implications. It is this fear which is driving us to develop alternatives for the current energy sources. One of the various ways to compare those sources is the Energy Return On Investment sometimes called EROI. It is simply the energy delivered by an energy obtaining activity compared to the energy required to get it. This approach is very useful for looking at the advantages and disadvantages of a given fuel and offers the possibility of looking into future in a different way by giving a great deal of information. If an energy resource requires more fuel to create as is gained from its development then that is probably by itself sufficient reason to recommend against its production. EROI by itself is not a sufficient criterion to make a complete decision about the use of various energy sources, but it gives a preliminary analysis of efficacy of the whole process of extraction of energy from a source and its use.
The idea of EROI was first formally put forth by Dr. Charles Hall, professor, State University of New York, through his PhD dissertation. The concept of EROI can be used to assess the production of oil in the United States. In 1930 the EROI for oil was at least 100 barrels returned for each barrel invested (i.e. EROI = >100:1), but declined to about 30:1 in 1970 to from 11 to 18: 1 in 2000 and is steadily decreasing by the increase in spending in exploration processes. (Cleveland et al. 1984, Hall et al. 1986, Cleveland 2004). The oil extracted from an offshore reservoir consumes more energy than what is recovered from onshore. Thus even if we have oil reserves if it costs more energy to extract than what it gives, then it is not a logical judgment to extract it. The problem with the extraction of oil shale is the same. The idea is clearer with the computation of EROI for corn derived ethanol. Most of the researchers, notably Pimentel and Patzek, state that it requires more energy for its production than what it delivers. Others state that corn derived ethanol has an energy surplus with an EROI of 1.2:1 to 1.6:1. Dr. Hall in his paper writes that for an economically viable use of a fuel its EROI should be much more than just 1. He says it might be close to 5:1(not proved though).
Importance of EROI:
Most of our policy issues regarding energy are based on monetary units. This does not allow us to forecast the use of particular energy source. That is the reason in America we have a low production and high consumption. We can think about each process in the units of energy and ultimately express each process in terms of EROI. This can give a much better insight into what the costs are relative to the gains in the future. It also helps to evaluate economical viability of different alternative fuels. Figure 1 gives an estimate of EROI for various sources. Even though the EROI for wind energy is high 20:1 the magnitude of energy available is less. Thus EROI for a single source can be different with respect to location. The return on investment for a particular source in America may be different from what in Europe. EROI can include the total magnitude of resources, which can ultimately indicate which fuels are likely to be able to make significant on US energy resources. EROI can also include environmental issues in the energy calculation.
Difficulties in calculating EROI:
In theory the calculation seems simple but it is complicated in application. Firstly the quality of the fuel is not taken into account in calculation. Thus cannot compare a low quality fuel with a higher quality one. For example, energy in the form of coal could be used in the production of ethanol. This might give an EROI less than one but the process could be desirable due to the benefits of liquid fuel (higher quality). Also the boundary for the energy input is not well defined. For example if one needs to calculate EROI of oil extraction and if steel is being used to drill for oil then should we add the energy input for the construction of steel or not? This complicates the calculation and sometimes data may not be available for the calculation. The methods for calculating EROI are still not clear but a lot of research is going on in developing a method which can rectify the above mentioned shortcomings. I think the Government can solve these difficulties by forming a research group or fund people who are doing research in this area.