Effects of Spatial Scale on Life Cycle Inventory Results

Closing Greenhouse Gas Emission Gaps of Staple Crops in China

China is facing the dual challenge of achieving food security and agricultural carbon neutrality. Developing spatially explicit crop emission profiles can help inform policy to mitigate agricultural greenhouse gases (GHGs), but previous life-cycle studies were conducted mostly at national and provincial levels. Here, we estimate county-level carbon footprint of China's wheat and maize production based on a nationwide survey and determine the contribution of different strategies to closing regional emission gaps. Results show that crop carbon footprint varies widely between regions, from 0.07 to 3.00 kg CO₂e kg^-1 for wheat and from 0.09 to 2.30 kg CO₂e kg^-1 for maize, with inter-county variation generally much higher than interprovince variation. Hotspots are mainly concentrated in Xinjiang and Gansu provinces, owing to intensive irrigation and high plastic mulch and fertilizer inputs. Closing the regional emission gaps would benefit mostly from increasing crop yields and nitrogen use efficiency, but increasing manure use (e.g., in Northeast, East, and Central China) and energy use efficiency (e.g., in North and Northwest China) can also make important contributions. Our county-level carbon footprint estimates improve upon previous broad-scale results and will be valuable for detailed spatial analysis and the design of localized GHG mitigation strategies in China.

A Commodity Supply Mix for More Regionalized Life Cycle Assessments

Supply chain information is invaluable to further regionalize product life cycle assessments (LCAs), but detailed information linking production and consumption centers is not always available. We introduce the commodity supply mix (CSM) defined as the trade-volume-weighted average representing the combined geographic areas for the production of a commodity exported to a given market with the goal of (1) enhancing the relevance of inventory and impact regionalization and (2) allocating these impacts to specific markets. We apply the CSM to the Brazilian soybean supply chain mapped by Trase to obtain the mix of ecoregions and river basins linked to domestic consumption and exports to China, EU, France, and the rest of the world, before quantifying damage to biodiversity, and water scarcity footprints. The EU had the lowest potential biodiversity damage but the largest water scarcity footprint following respective sourcing patterns in 12 ecoregions and 18 river basins. These results differed from the average impact scores obtained from Brazilian soybean production information alone. The CSM can be derived at different scales (subnationally, internationally) using existing supply chain information and constitutes an additional step toward greater regionalization in LCAs, particularly for impacts with greater spatial variability such as biodiversity and water scarcity.

Promoting potato as staple food can reduce the carbon–land–water impacts of crops in China

China has recently implemented a policy to promote potato as a national staple food and to close its large yield gaps with other countries. The carbon-land-water implications of this policy are examined here by compiling and analysing detailed city-level life-cycle inventories of China's staple crops. We find that in general potato, despite relatively low yields, has lower greenhouse gas emissions and water demand than other staple crops (maize, wheat and rice) on a per-calorie basis, but substantial regional variation exists for each crop. Integrating potato as a staple in China to meet increases in food demand and close the yield gap has the potential to reduce the total carbon-land-water impacts of staple crops by 17-25% by 2030. However, an unsuccessful integration runs the risk of global burden-shifting if the policy, for example, reduced domestic rice production and led to increased rice imports. Potential synergies between food security and environmental sustainability in China can be created by the potato policy, but greater efforts are needed to promote potato across the entire food supply chain from production to consumption.

The Environmental Consequences of Electrifying Space Heating

Decarbonization may require the efficient electrification of applications, like natural gas furnaces for space heating, that currently involve burning fossil fuels. The environmental consequences of such a fuel switch depend on location and time. Here we show that, in most parts of the U.S., a switch from natural gas to electric heat pumps would raise household heating bills and increase damages from carbon dioxide (CO₂) and other pollutants. For single-family homes in 658 of the 883 locations we analyze, a shift to heat pumps would increase annual hourly peak demand for electricity. For 265 of these 658 locations peak demand already occurred in winter; for the remaining 393 heat pumps would shift peak demand from summer to winter. An economy-wide tax on CO₂ emissions designed to substantially decarbonize electricity generation would make a switch to heat pumps beneficial for the environment and make electrified heating cheaper than burning natural gas. However, a sufficiently large tax would increase heating bills in cold parts of the country much more than in places with more moderate climates, even while making electric heat pumps cheaper to operate than natural gas furnaces. This differential impact raises questions about the feasibility of a carbon tax that is returned to each citizen as a uniform dividend.

Life cycle environmental impacts of food away from home and mitigation strategies-a review

Food production and consumption are major drivers of global environmental change, endangering the safe operating space of many environmental areas. Globally, there has been a growing trend of dining out, termed food away from home (FAFH) here, but its environmental sustainability has received insufficient attention. In this review, we examine studies quantifying the life-cycle environmental impacts of FAFH and identify mitigation strategies across the food supply chain. Overall, previous life cycle assessment (LCA) studies focused on the composition of FAFH meals and pre-use life cycle stages, especially food production. Greenhouse gas (GHG) emissions of FAFH meals range from 0.134 kg CO₂ e/meal to 13.2 kg CO₂ e/meal for school canteen meals, and from 0.60 kg CO₂ e/meal to 9.6 kg CO₂ e/meal for other catering services. Meat ingredients are the dominant source in a variety of environmental impact categories, and the food production stage usually accounts for over half of the total GHG emissions in the FAFH life cycle. Supply side mitigation strategies include advancing farming practices, updating cold transportation technology, and improving building energy efficiency. Demand side mitigation focuses on dietary change towards meals with less meat ingredients, with nudging and sustainable menu-designing as the two primary groups of strategies. Areas of focus for LCA include improving modeling of building energy consumption related to food consumption, advancing uncertainty characterization of life cycle results, and capturing geographical variations in food production.