Natural climate solutions pathways to achieving net zero emissions in Maine

Abstract:

Maine has goals to reduce gross greenhouse gas (GHG) emissions by 80% by 2050 and to be ‘net zero’ by 2045. Natural climate solutions (NCS) that sequester carbon or limit GHG emissions can affect near-term mitigation goals in cost-effective ways and enhance long-term ecosystem services. To date, most NCS studies are at a global or national scale, and state-level estimates are often reliant on assumptions more applicable elsewhere. Maine-specific analyses will inform the state climate action plan, enhance effective implementation of NCS practices, and provide an accessible way for stakeholders to evaluate and prioritize options.

The main objective of this study was to estimate the GHG mitigation benefit and costs of implementing NCS practices in Maine’s forest and agricultural sectors. We used a mixed methods approach that integrated biophysical and economic modeling to estimate the changes in harvest and yields, profits, revenue, GHG emissions, and carbon sequestration for several NCS practices relative to business as usual over the next 50 years.

We found that most forest management NCS practices can be implemented in Maine at a cost of $10-20/tCO₂e, which is relatively inexpensive compared to most non-NCS opportunities. Increasing the intensity of active forest management could yield about 4.5 MtCO₂e/yr in additional carbon sequestration at a cost of $14/tCO₂e, which was more effective than lengthening rotations. All scenarios have minimal leakage, while some also generated additional ecosystem services benefits. For agriculture, farmers could collectively amend their soil with biochar, reduce their tillage intensity, plant riparian buffers, and construct and utilize anaerobic digesters to manage dairy manure waste, thereby mitigating up to 0.8 MtCO₂e/yr in GHG emissions, about double the sector’s current annual emissions. This combined approach is estimated to cost $34/tCO₂e. Collectively, we found that implementing NCS practices at this scale can make Maine the first net zero GHG emissions state in the U.S. Further, our approach and findings can be applied to similar states throughout the country.