AAPG ANNUAL CONFERENCE AND EXHIBITION
Making the Next Giant Leap in Geosciences
April 10-13, 2011, Houston, Texas, USA
Sustainable Use of Fossil Energy
(1) Colorado Energy Research Institute, Colorado School of Mines, Golden, CO.
Finding common measures to compare and contrast multiple environmental impacts of fossil and renewable energy is challenging. A quantitative comparison of emissions by resource may be a good place to start. Power plants burning lignite coals emit by far the largest amount of CO2 for every unit of electricity produced (about 1200 tons of CO2 per GWhr of electricity). Bituminous coals emits about 2/3s as much, natural gas about 1/3. Renewable energy resources range from a high of 100 tons per GWhr of electricity down to 10 tons for some wind systems. So, if the goal is simply to reduce emissions - at all costs - the choice is easy: with only renewable (and nuclear) energy systems we may reduce CO2 emissions by more than 2 orders of magnitude for the same output of power.
Another measure is power density: how much land (or sea) area does it take to produce electricity from different resources? The densest power resource of all, oil shale, may yield 100 GW per km2 (while the resource lasts ~ decades), oil fields may yield 10 GW per km2, and a bituminous coal field may yield 1 GW per km2. Solar and geothermal power plants provide about 100 MW per km2, wind perhaps 10, and biomass less than 1. So, if one looks at optimizing the future global power supply from a land use perspective, the choice is very different: by using the most dense hydrocarbon accumulations on earth, the acreage used for power production would be 5 orders of magnitude less than the ‘worst’ renewable energy systems, for the same power output.
These numbers imply that climate stabilization without costly competition for arable land requires creative strategies for CO2 emissions reductions from fossil fuels. One such strategy is fuel shift from coal to natural gas, with its attendant lower emissions during combustion and much lower energy cost during production and shipping. Another is to decarbonize the planet’s huge volume of unconventional fossil energy resources (oil shale, shale oil, heavy oils, tight gas, shale gas, CBM, hydrates). Research is already underway on microbial, genetic engineering and catalytic approaches to break the long molecules of these unconventional hydrocarbons and produce only the lightest components: light oils and natural gas, and dramatically reduce the carbon footprint relative to current practices. There will still be a need for CCS technologies, to capture and store the CO2 from what might be a fossil energy industry run mostly on gas.