Chad M. Hellwinckel

Cropland carbon fluxes in the United States: increasing geospatial resolution of inventory-based carbon accounting.

Net annual soil carbon change, fossil fuel emissions from cropland production, and cropland net primary production were estimated and spatially distributed using land cover defined by NASAs moderate resolution imaging spectroradiometer (MODIS) and by the USDA National Agricultural Statistics Service (NASS) cropland data layer (CDL). Spatially resolved estimates of net ecosystem exchange (NEE) and net ecosystem carbon balance (NECB) were developed. The purpose of generating spatial estimates of carbon fluxes, and the primary objective of this research, was to develop a method of carbon accounting that is consistent from field to national scales. NEE represents net on-site vertical fluxes of carbon. NECB represents all on-site and off-site carbon fluxes associated with crop production. Estimates of cropland NEE using moderate resolution (approximately 1 km2) land cover data were generated for the conterminous United States and compared with higher resolution (30-m) estimates of NEE and with direct measurements of CO2 flux from croplands in Illinois and Nebraska, USA. Estimates of NEE using the CDL (30-m resolution) had a higher correlation with eddy covariance flux tower estimates compared with estimates of NEE using MODIS. Estimates of NECB are primarily driven by net soil carbon change, fossil fuel emissions associated with crop production, and CO2 emissions from the application of agricultural lime. NEE and NECB for U.S. croplands were -274 and 7 Tg C/yr for 2004, respectively. Use of moderate- to high-resolution satellite-based land cover data enables improved estimates of cropland carbon dynamics.

Energy use and carbon dioxide emissions from cropland production in the United States, 1990-2004.

Changes in cropland production and management influence energy consumption and emissions of CO(2) from fossil-fuel combustion. A method was developed to calculate on-site and off-site energy and CO(2) emissions for cropping practices in the United States at the county scale. Energy consumption and emissions occur on-site from the operation of farm machinery and occur off-site from the manufacture and transport of cropland production inputs, such as fertilizers, pesticides, and agricultural lime. Estimates of fossil-fuel consumption and associated CO(2) emissions for cropping practices enable (i) the monitoring of energy and emissions with changes in land management and (ii) the calculation and balancing of regional and national carbon budgets. Results indicate on-site energy use and total energy use (i.e., the sum of on-site and off-site) on U.S. croplands in 2004 ranged from 1.6 to 7.9 GJ ha(-1) yr(-1) and from 5.5 to 20.5 GJ ha(-1) yr(-1), respectively. On-site and total CO(2) emissions in 2004 ranged from 23 to 176 kg C ha(-1) yr(-1) and from 91 to 365 kg C ha(-1) yr(-1), respectively. During the period of this analysis (1990-2004), national total energy consumption for crop production ranged from 1204 to 1297 PJ yr(-1) (Petajoule = 1 x 10(15) Joule) with associated total fossil CO(2) emissions ranging from 21.5 to 23.2 Tg C yr(-1) (Teragram = 1 x 10(12) gram). The annual proportion of on-site CO(2) to total CO(2) emissions changed depending on the diversity of crops planted. Adoption of reduced tillage practices in the United States from 1990 to 2004 resulted in a net fossil emissions reduction of 2.4 Tg C.

Land Use Implications of Expanding Biofuel Demand

The Renewable Fuel Standard mandates in the Energy Independence and Security Act of 2007 will require 36 billion gallons of ethanol to be produced in 2022. The mandates require that 16 of the 36 billion gallons must be produced from cellulosic feedstocks. The potential land use implications resulting from these mandates were examined using two methods, the POLYSYS model and a general equilibrium model. Results of the POLYSYS analysis indicated that 72.1 million tons of corn stover, 23.5 million tons of wheat straw, and 24.7 million acres would be used to produce 109 million tons of switchgrass in 2025 to meet the mandate. Results of the CGE analysis indicated that 10.9 billion bushels of corn grain, 71 million tons of corn stover, and 56,200 tons of switchgrass is needed to meet the mandate.

Economic and environmental impacts of the corn grain ethanol industry on the United States agricultural sector

This study evaluated the impacts of increased ethanol production from corn starch on agricultural land use and the environment in the United States. The Policy Analysis System simulation model was used to simulate alternative ethanol production scenarios for 2007 through 2016. Results indicate that increased corn ethanol production had a positive effect on net farm income and economic wellbeing of the US agricultural sector. In addition, government payments to farmers were reduced because of higher commodity prices and enhanced net farm income. Results also indicate that if Conservation Reserve Program land was converted to crop production in response to higher demand for ethanol in the simulation, individual farmers planted more land in crops, including corn. With a larger total US land area in crops due to individual farmer cropping choices, total US crop output rose, which decreased crop prices and aggregate net farm income relative to the scenario where increased ethanol production happened without Conservation Reserve Program land. Substantial shifts in land use occurred with corn area expanding throughout the United States, especially in the traditional corn-growing area of the midcontinent region. Production of other crops, such as soybeans and cotton, shifted out of traditional growing areas to accommodate increased corn production. Fertilizer and chemical usage also increased. When conservation tillage adoption was assumed to remain at 2007 levels for the 10-year period, regional tillage intensity, soil erosion, and fossil fuel-based carbon emissions increased, while soil carbon stocks decreased as a result of increased corn production. However, the simulation demonstrated that additional adoption of conservation tillage above 2007 levels mitigated the adverse effects of increased corn production on soil erosion and net carbon emissions to the atmosphere.

Agricultural Impacts of Biofuels Production

Analysis of the potential to supply 25% of projected 2025 U.S. transportation fuels indicates sufficient biomass resources are available to meet increased demand while simultaneously meeting food, feed, and export needs. Corn and soybeans continue to be important feedstocks for ethanol and biodiesel production, but cellulose feedstocks (agricultural crop residues, energy crops such as switchgrass, and forestry residues) will play a major role. Farm income increases, mostly because of higher crop prices. Increased crop prices increase the cost of producing biofuels.

Evaluating possible cap and trade legislation on cellulosic feedstock availability

An integrated, socioeconomic–biogeophysical model is used to analyze the interactions of cap‐and‐trade legislation and the Renewable Fuels Standard. Five alternative policy scenarios were considered with the purpose of identifying policies that act in a synergistic manner to reduce carbon emissions, increase economic returns to agriculture, and adequately meet ethanol mandates. We conclude that climate and energy policies can best be implemented together by offering carbon offset payments to conservation tillage, herbaceous grasses for biomass, and by constraining crop residue removal for ethanol feedstocks to carbon neutral level. When comparing this scenario to the Baseline scenario, the agricultural sector realizes an economic benefit of US

Simulated impact of the renewable fuels standard on US Conservation Reserve Program enrollment and conversion

156 billion by 2030 and emissions are reduced by 135 Tg C‐equivalent (Eq) yr−1. Results also indicate that geographic location of cellulosic feedstocks could shift significantly depending on the final policies implemented in cap and trade legislation. Placement of cellulosic ethanol facilities should consider these possible shifts when determining site location.

Developing an amenity value calculator for urban forest landscapes

A socioeconomic model is used to estimate the land‐use implications on the U.S. Conservation Reserve Program from potential increases in second‐generation biofuel production. A baseline scenario with no second‐generation biofuel production is compared to a scenario where the Renewable Fuels Standard (RFS2) volumes are met by 2022. We allow for the possibility of converting expiring CRP lands to alternative uses such as conventional crops, dedicated second‐generation biofuel crops, or harvesting existing CRP grasses for biomass. Results indicate that RFS2 volumes (RFS2‐v) can be met primarily with crop residues (78% of feedstock demand) and woody residues (19% of feedstock demand) compared with dedicated biomass (3% of feedstock demand), with only minimal conversion of cropland (0.27 million hectares, <1% of total cropland), pastureland (0.28 million hectares of pastureland, <1% of total pastureland), and CRP lands (0.29 million hectares of CRP lands, 3% of existing CRP lands) to biomass production. Meeting RFS2 volumes would reduce CRP re‐enrollment by 0.19 million hectares, or 4%, below the baseline scenario where RFS2 is not met. Yet under RFS2‐v scenario, expiring CRP lands are more likely to be converted to or maintain perennial cover, with 1.78 million hectares of CRP lands converting to hay production, and 0.29 million hectares being harvested for existing grasses. A small amount of CRP is harvested for existing biomass, but no conversion of CRP to dedicated biomass crops, such as switchgrass, are projected to occur. Although less land is enrolled in CRP under RFS2‐v scenario, total land in perennial cover increases by 0.15 million hectares, or 2%, under RFS2‐v. Sensitivity to yield, payment and residue retention assumptions are evaluated.

Estimating Regional Changes in Soil Carbon with High Spatial Resolution

Abstract The goal of this research is to develop a framework that can be used by landscape and urban planners to implement an “amenity value calculator” for urban forest landscapes across a metropolitan county. By balancing the pros and cons of using typical hedonic frameworks versus urban forest inventory and management software systems, we (1) construct a data-driven approach to estimate the total amenity value associated with access to, views of, and existence of a particular forest landscape from among all available forest sites in a community and (2) develop a framework for an amenity value calculator for numerous community forest landscapes within a metropolitan county, using the amenity values generated from objective (1), that can be accessed and understood by anyone who is interested in the benefits provided by nearby community forests. Our research suggests that (i) residential household’s amenity value per acre of forest landscape decreases asymptotically towards zero as the driving time from a residential house increases, (ii) an amenity value calculator can be developed to sum the amenity values across all detached single-family houses within a range of driving times from any selected forest landscape, and (iii) a user-friendly, web-based application, that allows users to view the estimated amenity values of forest landscapes that interest them, can be created to better inform the public about the values of forest landscapes of interest to them.