Reducing Greenhouse Gas Emissions: Lessons from Case Studies

Efforts to ensure a nature-positive built environment must identify plausible scenarios for greenhouse gas (GHG) emissions reductions. There is a rich literature of planning studies seeking to identify and evaluate various scenarios for GHG emissions reductions. These planning studies are conducted on a range of scales from international, to national, to state, to local. This chapter reviews a set of GHG emissions reduction planning studies from the period of 2014 through 2019. Most planning efforts have concluded that dramatic emissions reductions are feasible. Efforts to reduce greenhouse gas emissions (referred to as “carbon abatement”) rely on some mixture of the following strategies: (1) demand reduction via energy efficiency measures such as more efficient equipment and more insulated buildings, (2) electrification of cooking, space heating, and water heating, coupled with low GHG electricity generation, (3) adoption of low GHG fuels such as hydrogen produced from renewables. The mixture of these three strategies varies from study to study. A detailed cost study in Philadelphia concluded that GHG abatement costs for energy efficiency measures vary dramatically by building with some cases showing negative abatement costs (i.e., utility saving were sufficient to pay for upfront investment without consideration of greenhouse gas emissions reductions) and others requiring large investments that would likely not be feasible for their owners. In particular, low and mid-rise residences were not particularly attractive for retrofits with abatement costs exceeding $200 per tonne of carbon dioxide. Switching current electricity uses to low GHG electricity had an estimated cost of $23/tonne abated. However, reducing GHG emissions from building heating presents a greater challenge as most buildings currently rely on gas heating and hence electrification requires a substantial capital investment in heat pumps, as well as the capital investment in low GHG electricity generation and storage capabilities. A study found that in New York City, abatement costs for switching to heat pumps ranged from roughly $125 to $160/tonne. The role for low GHG fuels in emissions reductions remains uncertain and contested with many studies seeing electrification as providing the bulk of emissions reductions with an important niche role for low GHG fuels. While the optimal pathway remains uncertain, a wide range of studies concur in their conclusions that substantial reductions in emissions are technically and economically feasible.