Straw-return methods that neither negatively impact yield nor bring environmental risk are ideal patterns. To attain this goal, it is necessary to conduct field observation to evaluate the environmental influence of different straw-return methods. Therefore, we conducted a 2-year field study in 2015–2017 to investigate the emissions of methane (CH₄) and nitrous oxide (N₂O) and the changes in topsoil (0–20 cm) organic carbon (SOC) density in a typical Chinese rice-wheat rotation in the Eastern China. These measurements allowed a complete greenhouse gas accounting (net GWP and GHGI) of five treatments including: FP (no straw, plus fertilizer), FS (wheat straw plus fertilizer), FB (straw-derived biochar plus fertilizer), FSDI (wheat straw with straw-decomposing microbial inoculants plus fertilizer) and CK (control: no straw, no fertilizer). Average annual SOC sequestration rates were estimated to be 0.20, 0.97, 1.97 and 1.87 t C ha⁻¹ yr⁻¹ (0–20 cm) for the FP, FS, FB and FSDI treatments respectively. Relative to the FP treatment, the FS and FSDI treatments increased CH₄ emissions by 12.4 and 17.9% respectively, but decreased N₂O emissions by 19.1 and 26.6%. Conversely, the FB treatment decreased CH₄ emission by 7.2% and increased N₂O emission by 10.9% compared to FP. FB increased grain yield, but FS and FSDI did not. Compared to the net GWP (11.6 t CO₂-eq ha⁻¹ yr⁻¹) and GHGI (1.20 kg CO₂-eq kg⁻¹ grain) of FP, the FS, FB and FSDI treatments reduced net GWP by 12.6, 59.9 and 34.6% and GHGI by 10.5, 65.8 and 37.7% respectively. In rice-wheat systems of eastern China, the environmentally beneficial effects of returning wheat straw can be greatly enhanced by application of straw-decomposing microbial inoculants or by applying straw-derived biochar.

Following formative work in the 1970s, disappearance in the 1980s, and reemergence in the 1990s, a chronological review shows that the past decade has witnessed increasing interest in the study of urban metabolism. The review finds that there are two related, non-conflicting, schools of urban metabolism: one following Odum describes metabolism in terms of energy equivalents; while the second more broadly expresses a city’s flows of water, materials and nutrients in terms of mass fluxes. Four example applications of urban metabolism studies are discussed: urban sustainability indicators; inputs to urban greenhouse gas emissions calculation; mathematical models of urban metabolism for policy analysis; and as a basis for sustainable urban design. Future directions include fuller integration of social, health and economic indicators into the urban metabolism framework, while tackling the great sustainability challenge of reconstructing cities.

Currently the land use and land use change (LULUC) emits 1.3 ± 0.5 Pg carbon (C) year⁻¹, equivalent to 8% of the global annual emissions. The objectives of this study were to quantify (1) the impact of LULUC on greenhouse gas (GHG) emissions in a subtropical region and (2) the role of conservation agriculture to mitigate GHG emissions promoting ecosystem services. We developed a detailed IPCC Tier 2 GHG inventory for the Campos Gerais region of southern Brazil that has large cropland area under long-term conservation agriculture with high crop yields. The inventory accounted for historical and current emissions from fossil fuel combustion, LULUC and other minor sources. We used Century model to simulate the adoption of conservation best management practices, to all croplands in the region from 2017 to 2117. Our results showed historical (1930–2017) GHG emissions of 412 Tg C, in which LULUC contributes 91% (376 ± 130 Tg C), the uncertainties ranged between 13 and 36%. Between 1930 and 1985 LULUC was a major source of GHG emission, however from 1985 to 2015 fossil fuel combustion became the primary source of GHG emission. Forestry sequestered 52 ± 24 Tg C in 0.6 Mha in a period of 47 years (1.8 Tg C Mha⁻¹ year⁻¹) and no-till sequestered 30.4 ± 24 Tg C in 2 Mha in a period of 32 years (0.5 Tg C Mha⁻¹ year⁻¹) being the principal GHG mitigating activities in the study area. The model predictions showed that best management practices have the potential to mitigate 13 years of regional emissions (330 Tg C in 100 years) or 105 years of agriculture, forestry and livestock emissions (40 Tg C in 100 years) making the agriculture sector a net carbon (C) sink and promoting ecosystem services.

Green areas cool the climate of a city, reduce the energy consumption caused by the urban heat island (UHI) effect, and bring along carbon savings. However, the calculation of carbon savings due to the cooling effect of green areas is still not well understood. We have used a Landsat Enhanced Thematic Mapper Plus (ETM+) image of Beijing, to identify the cooled areas, compute the possible energy used to maintain the temperature differences between cooled areas and their surrounding heated areas, and calculate the carbon savings owing to the avoidance of energy use. Results show that a total amount of 14315.37 tons carbon savings was achieved in the study area and the amount was related to the biomass, the size and the shape of green areas. These results demonstrate the importance of carbon savings resulting from green areas' cooling effect.

The two biggest environmental issues the world is currently dealing with are global warming and climate change. Minimizing energy consumption will help to cut down on greenhouse gas emissions, which is our responsibility. Companies choose ‘Carbon Footprint’ as a tool to calculate greenhouse gas emissions to show the impact of their activities on the environment. The techniques and procedures used in the analysis of carbon footprints are the primary focus of this study. Several criteria for evaluating carbon footprints were compared to one another to uncover parallels, variances, and deficiencies. Carbon footprints of companies and items were analyzed, and their objectives, ideas, topics of inquiry, calculation techniques, data choices, and additional elements were investigated. Standards for both organizations (ISO14064 and the GHG protocol) and products were compared and contrasted to arrive at accurate carbon footprint estimates. The most important aspects of a carbon footprint and assessment criterion are the research of GHG, system settings, measurement and carbon footprint, date, and treatment of individual emissions. Especially true for commercial enterprises and consumer goods. Guidelines have been produced for these challenges based on valuation criteria that have been used up to this point; nonetheless, they should be enhanced. This study highlights the need to formulate policies to reduce greenhouse gas emissions.

In recent years, green roofs have become the subject of increasing interest because of their good aesthetic qualities, energy conservation, and ability to reduce thermal island effect and absorb greenhouse gases, especially carbon dioxide (CO₂). Given the typically significant carbon emission of construction activities, adding any extra component to a structure increases the amount of carbon to be released during the execution stage. This also applies to green roofs, which require more materials and more extensive construction activities than traditional roofs. However, plants of green roofs absorb substantial amounts of CO₂ during their lifetime, thus leaving both short- and long-term positive impacts on the building’s carbon footprint. This study investigated the short- and long-term effects of green roofs on carbon footprint, as compared to conventional roofs. For this investigation, the CO₂ uptake of eight plant species with suitable drought- and cold-resistant properties was measured by infrared gas analysis (IRGA), and the effect of green roof on the building’s carbon footprint was analyzed using the software Design Builder. The results showed that building a green roof instead of a traditional roof increases the carbon emission of the construction process by 4.6 kg/m² of roof area. Investigations showed that, under high light intensities (1500–2000 μmol/m² s), Sedum acre L. has the best performance in compensating the extra carbon emission imposed on the construction process (in 264 days only). Under low light intensities (1000–1500 μmol/m² s), Frankenia laevis showed the best increase in the amount of carbon uptake (2.27 kg/m² year).

Although hybrid maize seed production is one of the most important agriculture systems worldwide, its greenhouse gas (GHG) emissions and potential mitigation measures have not been studied. In this study, we used life cycle assessment (LCA) to quantify the GHG emissions of 150 farmers run by 6 companies in an area of northwest China known for hybrid maize seed production. The results indicated that the average reactive nitrogen (Nr) losses and GHG emissions from hybrid maize seed production were 53 kg N ha⁻¹ and 8077 kg CO₂ eq ha⁻¹, respectively. Furthermore, the average nitrogen and carbon footprints of the process were 12.2 kg N Mg⁻¹ and 1495 kg CO₂ eq Mg⁻¹, respectively. Nitrogen fertilizer and electricity consumption for irrigation were the main contributors to high GHG emissions, accounting for 60% and 30% of the total, respectively. The GHG emissions from seed production for different companies varied greatly with their resource input. There was also a large variation in environmental burdens among the 150 farmers. Based on an analysis of the yield group, we found that the carbon footprint of the first group (the one with the highest yield) was 27% lower than the overall average. Scenario analysis suggests that a combined reduction of N input rate, optimizing irrigation, and increasing yield can eventually mitigate the carbon footprint of hybrid maize seed production by 37%. An integrated systematic approach (e.g., ISSM: integrated soil-crop system management) can reduce the GHG emissions involved in producing hybrid maize seeds. This study provides quantitative evidence and a potential strategy for GHG emissions reduction of hybrid maize seed production.

Carbon emission from pig production is an issue of great importance owing to its effect on global warming. Differed from widespread large-scale pig farms in North America and Europe, small-scale and smallholder pig farms are mainly concentrated in China. However, information on carbon emissions from Chinese smallholder pig farms is limited. Additionally, large amounts of drugs and vaccines have been applied during smallholder pig production in China, yet their contribution to carbon emissions is unclear. Therefore, detailed dataset which records all inputs during a pig’s entire life cycle should be obtained, so as to accurately determine the magnitude of carbon emissions from Chinese smallholder pig farms. This study took Yancheng, eastern China, as an example and adopted the carbon footprint (CF), life cycle inventory (LCI), and Intergovernmental Panel on Climate Change (IPCC) greenhouse gas (GHG) field calculations to accurately estimate the GHG emissions resulting from pig production of China. Furthermore, the contributions of vaccine application and other driving forces behind GHG emissions were identified using statistic methods. In the study area, the pig CFs in the nursery period, fattening period, and full life cycle were 5.83, 4.73, and 6.75 kg CO₂ eq·kg⁻¹ respectively. The CF of pig production in the study area varied from 4.74 to 9.48 kg CO₂ eq·kg⁻¹, with an average of 6.75 kg CO₂ eq·kg⁻¹; this average was, overall, higher than that of large-scale pig farms in North America and Europe. GHG emissions from manure (42.87%) and fodder (27.77%) were responsible for a large proportion of the total CF. Normal vaccine inputs contributed highly (15.33%) to the total CF. The contribution of vaccine application to the CF is roughly evaluated, suggesting it may be a potentially important source of GHG emissions in pig production and should receive more attention in the future. Furthermore, GHG emissions from smallholder pig production farms can be significantly reduced by developing a mixed crop-livestock system, increasing the application of organic fertilizers, and installing biogas digesters.

In recent years, the carbon footprint is regarded as the most important assessment tool of greenhouse gas emissions; it has attracted great attention of Chinese and foreign governments, enterprises, and relevant scholars. However, the comparative bibliometric analysis of Chinese and foreign articles on the carbon footprint research is still limited; thus, it has become the motivation of the present study. To quantitatively analyse the bibliometric differences between Chinese and foreign literature of the carbon footprint research, 673 Chinese articles and 3755 foreign articles between 2007 and 2020 were extracted from the Web of Science Core Collection database. On this basis, the publications, publishers, journals, authors, and institutions of Chinese and foreign articles were compared, and especially, the keyword and citation analysis results were obtained via the biblioshiny tool of bibliometrix R package. Results show that the output and influence of foreign articles are more prominent than Chinese articles in general. The foreign carbon footprint research is more systematic and mature than Chinese research, and both sides have some research topics of common concern and maintain their own research characteristics. Specific results may provide some reference for relevant researchers, policy makers, and the public.

Straw returning usually gives rise to greenhouse gas (GHG) emissions from the soil, and thus negatively affects carbon footprint (CF) of crop production. Numerous studies reported the effects of straw returning on the CF from single crop production. However, little is known about the integrated effects of different levels of straw returning on the CF and net ecosystem economic benefits (NEEB) from rice-wheat rotation. Here, we investigated the effects of different amounts of straw returning on soil CH₄ and N₂O emissions, GHG emissions from agricultural inputs (AIGHG), CF, and NEEB from a 2-year cycle of rice-wheat rotation. The CF was determined based on the total GHG emissions associated with crop production inputs and services. Overall, straw returning significantly increased annual CH₄ emissions by 5.4–72.2% and reduced annual N₂O emissions by 3.3–31.4% compared with straw removal. Straw returning remarkably increased rice grain yields by 8.1–9.9% and wheat grain yields by 10.2–21.1% compared with straw removal. The average annual AIGHG from rice-wheat rotation ranged from 3579 to 4987 kg CO₂-eq ha–¹. Diesel consumption played a dominant role in the AIGHG. The annual CF ranged from 0.96 to 1.31 kg CO₂-eq kg–¹ and increased with increasing straw returning amounts. The NEEB, which ranged from 14161 to 17413 CNY ha–¹, was significantly affected by the levels of straw returning. The treatment with returning of 1/3 of preceding crop straw to the field (2.19–2.47 kg ha⁻¹ year⁻¹ of rice straw in the wheat season and 1.38–1.68 kg ha⁻¹ year⁻¹ of wheat straw in the rice season) resulted in relatively higher grain yield, the lowest CF, and the highest NEEB among all treatments, and thus can reduce CF, and increase grain yields and NEEB, and thus can be recommended as a sustainable approach to mitigate GHG emissions and increase economic benefits from rice-wheat rotation.