From: Penn State
Published November 30, 2017 01:47 PM

Uncertainty Surrounds U.S. Livestock Methane Emission Estimates

A new study of methane emissions from livestock in the United States — led by a researcher in Penn State's College of Agricultural Sciences — has challenged previous top-down estimates.

The research was conducted because serious discrepancies exist between top-down estimates that suggest the U.S. Environmental Protection Agency is underestimating agricultural methane emissions by up to 90 percent, and bottom-up estimates accepted by the federal government showing lower emissions.

Top-down emissions estimates involve monitoring atmospheric methane concentrations by satellites or from air samples collected at high altitude by planes, and using models to estimate the sources of emissions. Bottom-up estimates take into account livestock populations and animal emission factors.

In their detailed analysis, researchers used a spatially explicit, bottom-up approach, based on animal inventories and feed-intake-based emission factors, to estimate enteric methane emissions for cattle and manure methane emissions for cattle, swine and poultry for the contiguous United States.

Read more at Penn State

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