Trends in Water Use, Energy Consumption, and Carbon Emissions from Irrigation: Role of Shifting Technologies and Energy Sources

Global energy use and carbon emissions from irrigated agriculture

Irrigation is a land management practice with major environmental impacts. However, global energy consumption and carbon emissions resulting from irrigation remain unknown. We assess the worldwide energy consumption and carbon emissions associated with irrigation, while also measuring the potential energy and carbon reductions achievable through the adoption of efficient and low-carbon irrigation practices. Currently, irrigation contributes 216 million metric tons of CO2 emissions and consumes 1896 petajoules of energy annually, representing 15% of greenhouse gas emissions and energy utilized in agricultural operations. Despite only 40% of irrigated agriculture relies on groundwater sources, groundwater pumping accounts for 89% of the total energy consumption in irrigation. Projections indicate that future expansion of irrigation could lead to a 28% increase in energy usage. Embracing highly efficient, low-carbon irrigation methods has the potential to cut energy consumption in half and reduce CO2 emissions by 90%. However, considering country-specific feasibility of mitigation options, global CO2 emissions may only see a 55% reduction. Our research offers comprehensive insights into the energy consumption and carbon emissions associated with irrigation, contributing valuable information that can guide assessments of the viability of irrigation in enhancing adaptive capacity within the agricultural sector.

The recovery potential and utilization pathway of chemical energy from wastewater pollutants during wastewater treatment in China

Research on the potential for chemical energy recovery and the optimization of recovery pathways in different regions of China is still lacking. This study aimed to address this gap by evaluating the potential and optimize the utilization pathways for chemical energy recovery in various regions of China for achieving sustainable wastewater treatment. The results showed that the eastern and northeastern regions of China exhibited higher chemical energy levels under the existing operating conditions. Key factors affecting chemical energy recovery included chemical oxygen demand removal (ΔCOD), treatment scale, and specific energy consumption (μ) of wastewater treatment plants (WWTPs). Furthermore, the average improvement in the chemical energy recovery rate with an optimized utilization pathway was approximately 40% in the WWTPs. The use of the net-zero energy consumption (NZE) model proved effective in improving the chemical energy recovery potential, with an average reduction of greenhouse gas (GHG) emissions reaching next to 95% in the investigated WWTPs.

Reducing energy and carbon footprint in semi-arid irrigated cropping systems through crop diversification

Energy and carbon (C) footprints of agricultural production practices have garnered high attention due to rising energy costs and increasing global warming. However, the contribution of conservation and regenerative farming practices, including cover cropping, on energy and C footprints have not yet been documented for cropping systems in arid and semi-arid regions. This study evaluated the energy and C footprint of cover crop integrated silage maize (Zea mays L.) and sorghum (Sorghum bicolor L. Moench) production systems in the semi-arid region of the southwestern US. The treatments were mixtures of winter cover crops: i) grasses and legumes (GL), ii) grasses, brassicas, and legumes (GBL), iii) grasses and brassicas (GB), and iv) no cover crops (NCC) control for each crop production system. Results showed cover crops had 24.1-24.5% greater energy input than NCC. In silage maize rotation, energy output was 17-22% greater in GBL and GL than in NCC. In silage sorghum rotation, the energy output was 15-24% greater in all cover crops than in NCC. The resulting net energy was 16-21% greater in GBL and GL than in NCC under silage maize, while it was 18-24% greater in GBL and GB than in NCC under silage sorghum. In the silage maize system, the C-footprint per kg yield was not different among treatments, whereas in silage sorghum, it was 58% greater in GBL than in NCC. The benefit-to-cost ratio was greater than one for all treatments, but the additional revenue through C credit programs could make cover cropping a more feasible and beneficial approach, improving economic and environmental sustainability while producing silage crops. While the C footprint was crop rotation specific, cover cropping should be encouraged over crop-fallow systems to producers in semi-arid environments to reduce energy usage and increase C-credit benefits. Clear national and state policy on the C credit program will also enhance economic and environmental benefits by adopting cover cropping and other regenerative farming practices.

Influence of energy poverty on agricultural water efficiency using a panel data study in China

The research attention is increasingly directed towards the effective integration of the 17 United Nations Sustainable Development Goals (SDGs) within the limitations of the real world and amidst intersectoral conflicts. In light of the inextricable relationship between irrigation and energy, the objective of this study is to identify potential avenues for achieving the SDG6 and SDG7 goals of enhancing water use efficiency in agriculture and eradicating energy poverty, respectively. Utilizing data from 30 Chinese provinces from 2002 to 2017, this study explores the dynamic influence of energy poverty on agricultural water efficiency with a system generalized method of moments methodology. The findings suggest that energy poverty may greatly reduce agricultural water efficiency. The heterogeneity study shows that when agricultural water efficiency grows, the negative impacts of energy poverty continue to fade. Based on an assessment of various processes, results suggest that non-farm employment and cropping structure modification is a prominent conduit via which energy poverty negatively influences agricultural water efficiency.

Greenhouse gas emissions from US irrigation pumping and implications for climate-smart irrigation policy

Irrigation reduces crop vulnerability to drought and heat stress and thus is a promising climate change adaptation strategy. However, irrigation also produces greenhouse gas emissions through pump energy use. To assess potential conflicts between adaptive irrigation expansion and agricultural emissions mitigation efforts, we calculated county-level emissions from irrigation energy use in the US using fuel expenditures, prices, and emissions factors. Irrigation pump energy use produced 12.6 million metric tonnes CO2e in the US in 2018 (90% CI: 10.4, 15.0), predominantly attributable to groundwater pumping. Groundwater reliance, irrigated area extent, water demand, fuel choice, and electrical grid emissions intensity drove spatial heterogeneity in emissions. Due to heavy reliance on electrical pumps, projected reductions in electrical grid emissions intensity are estimated to reduce pumping emissions by 46% by 2050, with further reductions possible through pump electrification. Quantification of irrigation-related emissions will enable targeted emissions reduction efforts and climate-smart irrigation expansion.

High soil carbon sequestration rates persist several decades in turfgrass systems: A meta-analysis

Managed turfgrass is a common component of urban landscapes that is expanding under current land use trends. Previous studies have reported high rates of soil carbon sequestration in turfgrass, but no systematic review has summarized these rates nor evaluated how they change as turfgrass ages. Here we conducted a meta-analysis of soil carbon sequestration rates from 63 studies globally, comprised mostly of C3 grass species in the U.S., including 24 chronosequence studies that evaluated carbon changes over 75 years or longer. We showed that turfgrass established within the last ten years had a positive mean soil C sequestration rate of 5.3 Mg CO₂ ha^-1 yr^-1 (95% CI = 3.7-6.2), which is higher than rates reported for several soil conservation practices. Areas converted to turfgrass from forests were an exception, sometimes lost soil carbon, and had a cross-study mean sequestration rate that did not differ from 0. In some locations, soil C accumulated linearly with turfgrass age over several decades, but the major trend was for soil C accumulation rates to decline through time, reaching a cross-study mean sequestration rate that was not different from 0 at 50 years. We show that fitting soil C timeseries with a mechanistically derived function rather than purely empirical functions did not alter these conclusions, nor did employing equivalent soil mass versus fixed-depth carbon stock accounting. We conducted a partial greenhouse gas budget that estimated emissions from mowing, N-fertilizer production, and soil N₂O emissions. When N fertilizer was applied, average maintenance emissions offset 32% of C sequestration in recently established turfgrass. Potential emission removals by turfgrass can be maximized with reduced-input management. Management decisions that avoid losing accrued soil C-both when turfgrass is first established and when it is eventually replaced with other land-uses-will also help maximize turfgrass C sequestration potential.

An Analysis of the Spatiotemporal Characteristics and Diversity of Grain Production Resource Utilization Efficiency under the Constraint of Carbon Emissions: Evidence from Major Grain-Producing Areas in China

As the most important driving force for ensuring the effective supply of grain in the country, the production stability of the major grain-producing areas directly concerns the national security of China. In this paper, considering the “water–soil–energy–carbon” correlation, water, soil and energy resource factors, and carbon emission constraints were included in an index system, and the global common frontier boundary three-stage super-efficient EBM–GML model was used to measure the grain production resource utilization efficiency of the major grain-producing areas in China from 2000 to 2019. This paper also analyzed the static and dynamic spatiotemporal characteristics and the restrictions of utilization efficiency. The results showed that, under the measurement of the traditional data envelopment analysis model, the grain production resource utilization efficiency in the major producing areas is relatively high, but there is still room to improve by more than 20%, and grain production still has enormous growth potential. After excluding external environmental and random factors, it was found that the utilization efficiency of grain production resources in the major producing areas decreased, and the efficiency and ranking of provinces changed significantly. External factors inhibit pure technical efficiency and expand the scale efficiency. The utilization efficiency of Northeast China was much higher than that of the Huang-Huai-Hai region and the middle and upper reaches of the Yangtze River region, and its grain production resource allocation management had obvious advantages. The total factor productivity index of food production resources showed an upward trend as a whole, and its change was affected by both technological efficiency and technological progress, of which technological progress had the greater impact. Therefore, reducing the differences in the external environment of different regions while making adjustments in accordance with their own potential is an effective way to further improve the utilization efficiency of food production resources.

Is It Possible to Reduce Agricultural Carbon Emissions through More Efficient Irrigation: Empirical Evidence from China

Although irrigation systems are critical to the long-term viability of agriculture, they also contribute a significant amount of carbon dioxide emissions. This creates a conflict between reducing greenhouse gas emissions and promoting agricultural growth. Researchers may be able to gain a better understanding of the subject by looking at the connection between irrigation water efficiency (IWE) and agricultural carbon emissions (ACE). With data from 30 Chinese provinces collected between 2002 and 2019, this study examines the dynamic effect of IWE on ACE. According to the results, IWE has the potential to significantly raise ACE. The positive effects of IWE become more pronounced as ACE increases, according to the heterogeneity analysis. ACE in northern China is also more vulnerable to IWE than other ACE regions. Irrigation scales appear to be a significant channel through which IWE positively affects ACE, according to an investigation of possible mechanisms. However, the increased IWE causes the planting structure adjustments, which aids in the reduction of ACE. The results of this study have significant ramifications for public policy.

Bibliometric Analysis of Groundwater’s Life Cycle Assessment Research

Groundwater is an important water resource that accounts for 30% of the world’s freshwater. 97% of this extracted groundwater is for drinking and human use. Due to anthropogenic activities, this resource is affected and, consequently, its life cycle is modified, changing its natural state. This paper aims to analyse the scientific production that deals with the study of groundwater’s Life Cycle Assessment (LCA), using bibliometric methods. Thus, it contributes to the evolution of knowledge of this resource in terms of its use (environmental, economic and social). The methodological process includes: (i) selection and analysis of search topics in the Scopus and Web of Science (WoS) databases; (ii) application of Bibliometrix and Visualisation of Similarity Viewer (VOSviewer) software to the data collected; (iii) scientific structure of the relation of the topics groundwater and life cycle, considering programme lines and relations in their sub-themes; (iv) literature review of Author keywords. A total of 780 papers were selected, 306 being from Scopus, 158 from WoS and 316 published in both databases. The time evolution of the analysed data (publications) indicates that groundwater LCA studies have seen exponential growth (between 1983 and 2021). In addition, it has three development periods: introduction (years between 1983 and 2001), growth (between 2002 and 2011) and maturation (between 2012 and 2021). At the country level (origin of contributions authors), the USA dominates the total scientific production with 24.7%, followed by Denmark with 12.8% and 10.3% for China. Among the main topics of study associated with LCA are those focused on: the proposal of remediation methods, the application and development of technologies and the use of water resources by the urban community. This study allows establishing new trends in agricultural development issues about irrigation efficiency, wastewater reuse, mining and treatment, climate change in a circular economy scheme related to sustainability and life cycle assessment.