Implications of regional N2O–N emission factors on sugarcane ethanol emissions and granted decarbonization certificates

Abstract

Reducing greenhouse gas (GHG) emissions by substituting fossil fuels depends on how biofuels are produced and how emissions are calculated. Nitrous oxide (N2O) emissions from synthetic and organic N fertilizers are important sources of GHG from sugarcane ethanol. This study aimed to synthesize the literature information and derive regional N2O emissions factors (EFs) for N fertilizers according to Tier 2 approach. This study also evaluated how the use of Tier 2 affects emissions compared with those obtained by the IPCC Tier 1. Moreover, this study examined how N fertilizers can affect GHG emissions and the earning of decarbonization certificates (CBIOs) by ethanol producers. For an ethanol distillery producing 339 million liters annually, the use of Tier 1 and Tier 2 resulted in emissions of 176.5 and 145.2 Gg CO2eq, whereas for the same amount of energy, gasoline would emit 661.8 Gg CO2eq. The addition of nitrification inhibitors (NIs) to N fertilizers and improvements in vinasse/fertilizer management further reduced emissions compared with Tier 2. In Tier 1, the GHG emission savings would result 485,270 CBIOs, worth 4.85 million US$ at US$10 per CBIO. But if the IPCC Tier 2 is considered, the annual CBIOs would be worth 5.17 million US$. Using NIs and improving vinasse/fertilizer management may bring an additional US$ 31,700 and US$ 48,000 revenue above that of Tier 2. Public and sectorial policies behind decarbonization certificates can encourage farmers and decision-makers to pursue more efficient and economical solutions to further decrease GHG emissions and improve the sustainability of ethanol.