BioCycle May 2012, Vol. 53, No. 5, p. 45
The US Department of Energy (DOE) recently released energy consumption numbers for the U.S. in 2011. Renewable energy consumption was up and total energy consumption stayed the same. The total share of renewable energy production grew to 9.3 percent of total energy used. That is up from 8.2 percent in 2010. Ten years ago the percent of renewable energy consumed in the U.S. was around 6 percent. We are learning to use less fossil fuel and as individuals are using less energy per year.
Total annual energy consumption estimated by DOE’s Energy Information Administration (EIA) was 97.6 quadrillion BTU (quad) in 2011. For the last 10 years, this use has averaged 98.6 quad, going over the 100 quad-mark in three of those years. For referencing purposes, the breakdown of the annual total energy consumption in quads is equivalent to the percent. For instance, the 9.3 percent of renewable energy references 9.13 quad out of 97.6 quad. At the opposite end of simplicity, it is important to stress that these numbers are so large they are difficult to grasp. One quadrillion BTUs is a 1 followed by 15 zeroes (1,000,000,000,000,000), or 1 percent of 100 quad.
Within that 9.1 quad of renewable energy, the major contributors were hydroelectric (35 percent), wood energy (22 percent), biomass (21 percent) and wind (13 percent). The remaining 10 percent is derived from wastes (e.g., landfill gas), geothermal and solar energy. The big change in this increase in renewable energy came from a large jump in hydroelectric power. Most of this change is not a result of new facilities, but from heavy rainfall during 2011. In other words, 60 percent of the 1 quad-increase in 2011 renewable energy consumption is attributed to gains from heavy rainfall. This means that the other renewable energy components only contributed 40 percent of the additional renewable energy quad.
Consumption Habits Over Time
The 10-year trend of these various renewable energy types is as interesting as the total output of each type. Wind energy has averaged 33 percent growth in consumption for the last 10 years. Biofuels have averaged 23 percent growth in consumption. Solar energy had the next highest average increase in consumption, averaging a 5 percent increase since 2000. However the last five years, since 2006, annual solar energy has averaged 19 percent. Solar energy consumption did not grow in the first half the decade, but has taken off the last half.
The other renewable energy sectors are less compelling. Geothermal has averaged a fairly steady 3 percent growth. Wood-derived energy has declined an average of 1 percent each year. This seemed inconsistent with the growth of wood pellet production. To validate the EIA declining wood fuel consumption, I found data on U.S. hearth appliance shipments (stoves and furnaces) on the Pellet Fuels Institute website. Apart from three good years, wood pellet stove sales have been steady at best. Cord wood stoves sales have dropped to nearly one-third of the volume that stoves were being sold 10 years prior. Wood stoves last a long time, so the drop in sales doesn’t necessarily mean a drop in consumption, but the significant decline is consistent with a drop in wood energy consumption.
Since 2000, waste fuels also have been declining. This also seemed inconsistent with the growth in landfill gas projects. Looking more closely at the waste consumption data shows that in the last five years, waste fuel consumption has had a fairly steady, 5 percent growth. It is just the 11-year average that shows no growth.
As mentioned earlier, the heavy rains have biased the hydropower energy consumption to be high. From 2000 to 2010, hydropower energy consumption experienced zero growth. Looking once more at the 40 percent of increased 2011 renewable energy consumption that did not come from hydroelectricity, there may be some encouraging news yet. Forty percent of non-hydroelectric power consumption is about 0.400 quad. This 2011 volume of energy is more than double the 10-year average increase in U.S. renewable energy growth, or 0.190 quad.
Energy Inputs Per Unit Of Human
From 1990 to 2000, U.S. annual energy consumption grew. Since 2000 though, annual energy consumption has been very stable at 100 quad/year. However, the U.S. population has continued to grow so energy consumption per person has actually been declining. During the decade of the 1990s the average annual U.S. per capita energy consumption was 345 million BTU (MMbtu). For the last five years, the average annual per capita consumption was 322 MMbtu. In 21 years that is a 9 percent reduction.
I have been living in the university towns of Davis, California and Columbia, Missouri where bicycle transportation is common. There are some estimated 40,000 bikes registered in Davis. Bicycle travel and walking are both bioenergy powered forms of travel, but are not included in the EIA numbers. I have not found a dataset yet that estimates miles traveled or fossil BTUs avoided from self-propulsion on a regional or national scale. Adding telecommuting to the list of fossil BTUs avoided would better illustrate the significant shifts in U.S. energy consumption that are taking place.
In summary, as a nation, our energy consumption has plateaued at 100 quad with steady increases in renewable energy. In 2011, energy consumption from renewables was up, and energy consumption on a per capita basis was declining. We have a long way to go, but the U.S. is making small but measurable gains in curbing its energy consumption.
Mark Jenner, PhD; World Agricultural Economic and Environmental Services (WAEES), California Biomass Collaborative, and Biomass Rules, LLC (www.biomassrules.com).