Over two million hectares of marginal land in the Northeast USA no longer used for agriculture may be suitable and available for production of second-generation cellulosic bioenergy crops, offering the potential for increased regional bioenergy production without competing with food production on prime farmland. Current yields of perennial bioenergy grasses and short-rotation woody crops range from 2.3 to 17.4 and 4.5 to 15.5 Mg/ha, respectively, and there is great potential for increased yields. Regional advantages for bioenergy development include abundant water resources, close proximity between production and markets, and compatibility of bioenergy cropping systems with existing agriculture. As New York and New England (a subset of the Northeast region) account for~85 % of the nation's heating oil consumption, production of bioheat, biopower, and combined heat and power could substantially reduce the region's dependence on imported petroleum. While numerous grassroots efforts are underway in the region across supply chains, bioenergy development faces several challenges and unknowns in terms of environmental impact, production, yields, socioeconomics, and policy. We explore the opportunities for second-generation bioenergy production on the unused marginal lands of the Northeast USA and discuss the challenges to be addressed to promote sustainable bioenergy production on the region's underutilized marginal land base.

Core Ideas We studied hotspots of nitrous oxide emission from perennial grasses on wet soil. Hotspots occurred in a limited range of soil moisture and temperature conditions. Hotspots recurred more frequently at specific places over a three year period. Hotspots of nitrous oxide (N2O) emission are thought to contribute substantially to annual emissions from agricultural soils. We observed N2O fluxes from fertilized and unfertilized C3 and C4 perennial grasses on a wet silt loam soil in New York, United States during the growing season in 2013, 2014, and 2015 using static chambers. Analysis of N2O hotspots within the research plots revealed that hotspots contributed between 34.3 and 39.1% of the total emissions, and constituted between 0.8% and 5.0% of all flux observations. Hotspots were more frequent and of greater magnitude in the fertilized treatments, and occurred when soil temperature was greater than 9.1°C and soil moisture was between about 40% and 80% water filled pore space (WFPS). A single chamber location in the fertilized switchgrass treatment was consistently a hotspot for N2O emission, suggesting that hotspots maintain a stable spatial pattern over extended periods. The maximum magnitude of N2O hotspot emission exhibited a relationship to soil temperature that is similar to that of the microbial growth rate constant.

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While agricultural practices are widely reported to contribute to anthropogenic greenhouse gas (GHG) emissions, there are only limited measurements available for emission rates in the monsoon climate of the African continent. We conducted a scoping study to measure nitrous oxide (N 2 O-N) and methane (CH 4 ) emission rates from 24 plots constructed on smallholder agricultural farms along the slope catena of three transects in the sub-humid Anjeni watershed in the Ethiopian highlands. Greenhouse gas flux samples were collected in 2013, before, towards the end, and after the rainy monsoon phase. At each location, three plots were installed in groups: two plots grown with barley (one enriched with charcoal and the other without soil amendment) and lupine was grown on the third plot without any soil amendment. Preliminary study results showed that nitrous oxide emission rates varied from −275 to 522 µg·m −2 ·h −1 and methane emissions ranged from −206 to 264 µg·m −2 ·h −1 with overall means of 51 and 5 µg·m −2 ·h −1 for N 2 O-N and CH 4 , respectively. Compared with the control, charcoal and lupine plots had elevated nitrous oxide emissions. Plots amended with charcoal showed on average greater methane uptake than was emitted. While this study provides insights regarding nitrous oxide and methane emission levels from smallholder farms, studies of longer durations are needed to verify the results.