Catchphrases, however tiresome their proliferation, can alert us to important issues. Take "carbon footprint,” an idea now routinely mentioned in corporate ads, political discourse, and environmental advocacy.
Recently a new and very important addition to the catchphrase glossary—lifecycle analysis—has morphed from academic writing to climate policy concerns. Indeed it is embodied in a number of current legislative proposals—among them the Waxman-Markey energy bill.
The concept, in principle, is straightforward. To calculate CO2 emissions associated with use of coal to produce electricity, you shouldn't just consider emissions during combustion in the power plant but also account for the energy (and CO2 emitted) in transporting the coal from mine to generating station. Or, you can't just revel in CO2 absorbed (through photosynthesis in the growth stage) to claim carbon "neutrality" when producing corn-based ethanol. You've got to account for how much energy is used in the ethanol distillery and, beyond that, how much (locked in) carbon is released from soil when planting corn. If such releases are large, they can negate the “offsets” designed to compensate for excess releases from conventional energy combustion activity.
The scope of how wide a net should be cast to catch indirect sources of emissions is anything but clear-cut. (In the case of ethanol land requirements may remove acreage devoted to food, whose cost may rise—yet one further indirect effect.) So, here we confront the dilemma of shifting from lifecycle costing as an analytical concept to a factor susceptible to unambiguous and enforceable policy and legislation. Indeed, a recent and widely-reported discord between Reps. Waxman and Peterson (respectively, Chairs of the House Energy and Commerce Committee and the Agriculture Committee) spotlights precisely concerns over the calculation of lifecycle biomass emissions and the appropriateness of EPA’s role as the monitoring agency.
Climate policy complications are not limited to carbon-containing resources. Non-CO2 greenhouse gases, while contributing less to global warming than carbon dioxide, cannot be ignored. They include methane, nitrous oxide, and a certain class of hydrofluorocarbons. (Combining the four into a single metric, denoted as “CO2e,” involves weights based on the potency of a particular gas, coupled to its residence time in the atmosphere.) Lifecycle and CO2e measurement can often figure jointly in a given situation. Production of fertilizer involves carbon-containing energy inputs like natural gas; application of fertilizer in farming can give rise to emissions of nitrous oxide. The carbon dioxide-equivalent measure gets us out of the apples-vs.-oranges bind.
Workable ways of dealing with the lifecycle and carbon dioxide-equivalence problems can no doubt be overcome. But we’re not there yet—neither in the case of domestic climate policy, nor in the more formidable task of harmonizing multi-country climate mitigation strategies.
An exhaustive body of data and information is contained in the EPA Inventory of U.S. Greenhouse Gas Emissions and Sinks: 1990-2007, April, 2009.
