In light of the environmental challenges currently facing humanity, the issue of the environmental sustainability of crop production is becoming increasingly pressing. This is due to the fact that global population growth and the related demand for food are placing significant pressure on the environment. Wheat is a strategic crop globally due to its extensive cultivation area, high production and consumption levels, and vital nutritional properties. It is cultivated across diverse climatic conditions and within various agricultural production systems. It is of the utmost importance to pursue sustainable wheat production on a global scale, given the necessity to protect the environment and climate. The application of life cycle assessment (LCA) enables the identification of potential avenues for enhancing wheat production processes, thereby reducing the negative environmental impacts associated with these processes. This paper presents a synthesis of the existing literature on the environmental LCA of wheat grain production. It compares the impacts of different production systems, highlights critical stages in wheat cultivation, and provides recommendations for sustainable practices and directions for future research.

Carbon dioxide removal (CDR) systems are an integral part of sustainable pathways limiting global warming to less than 2.0 °C. When the sole purpose of CDR is capturing and storing atmospheric CO2, carbon registries offer detailed procedures to calculate the carbon removal credits. However, the registries do not address how to distribute CO2 flows when CDR provides additional services. Standardized, transparent rules for distributing CO2 flows among CDR services are required for the formation of efficient private and public carbon markets. The lack of such rules could result in double counting if those reductions are allocated to more than one service, decreasing the trustworthiness of carbon removal credits or deterring the delivery of an additional low-carbon service, thus limiting the economic viability and deployment of CDR. We examine allocation rules in carbon registries and carbon accounting guidelines, including their life cycle assessment (LCA) principles. We evaluate physical (mass-based) and non-physical (economic) allocation methods using a generic CDR system and find both to be unworkable. We then develop a mass balance (MB) approach which can reliably allocate captured and stored carbon (CSC) between carbon removal credits and other services based on the value CO2 removal in those markets. This practical approach to allocation can be used in a transparent way to provide flexibility that would allow CDR services to capture the value of the multiple services they provide and, through this, promote the deployment of these sustainable alternatives.

Context. Climate change and water scarcity are global challenges facing humanity. Animal agriculture generates considerable greenhouse gas (GHG) emissions and consumes large volumes of water from rivers, streams and lakes. Reducing consumption of animal agricultural products with a relatively high carbon or water footprint, such as dairy, is often promoted as a mechanism to reduce the environmental impacts of food production. Attributionally-based footprints do not, however, assess the consequences of a change in demand for a product. Aims. This study aimed to assess the water and climate change consequences of replacing NSW dairy production, and co-products of dairy production, with plant-based alternatives. Methods. Process-based consequential life cycle assessment was used. Key results. Water savings associated with the change would be limited and GHG emissions reductions would be ~86% of that as estimated by the carbon footprint of production. When NSW dairy production was replaced with soy-based alternatives and two GHG emissions reduction strategies were implemented across the industry, namely enteric methane inhibitors and flaring methane from effluent ponds, GHG emissions increased by 0.63 Mt carbon dioxide equivalent when dairy production was replaced. Conclusions. The environmental benefits associated with replacing NSW dairy production with plant-based alternatives should not be determined by attributionally-based approaches. Implications. Policies that aim to reduce the environmental impacts of agricultural production need to consider the market effects of a change in demand for products and not rely on estimated impacts of current production.

The world's forests store large amounts of carbon (C), and growing forests can reduce atmospheric CO2 by storing C in their biomass. This has provided the impetus for world-wide tree planting initiatives to offset fossil-fuel emissions. However, forests interact with their environment in complex and multifaceted ways that must be considered for a balanced assessment of the value of planting trees. First, one needs to consider the potential reversibility of C sequestration in trees through either harvesting or tree death from natural factors. If carbon storage is only temporary, future temperatures will actually be higher than without tree plantings, but cumulative warming will be reduced, contributing both positively and negatively to future climate-change impacts. Alternatively, forests could be used for bioenergy or wood products to replace fossil-fuel use which would obviate the need to consider the possible reversibility of any benefits. Forests also affect the Earth's energy balance through either absorbing or reflecting incoming solar radiation. As forests generally absorb more incoming radiation than bare ground or grasslands, this constitutes an important warming effect that substantially reduces the benefit of C storage, especially in snow-covered regions. Forests also affect other local ecosystem services, such as conserving biodiversity, modifying water and nutrient cycles, and preventing erosion that could be either beneficial or harmful depending on specific circumstances. Considering all these factors, tree plantings may be beneficial or detrimental for mitigating climate-change impacts, but the range of possibilities makes generalisations difficult. Their net benefit depends on many factors that differ between specific circumstances. One can, therefore, neither uncritically endorse tree planting everywhere, nor condemn it as counter-productive. Our aim is to provide key information to enable appropriate assessments to be made under specific circumstances. We conclude our discussion by providing a step-by-step guide for assessing the merit of tree plantings under specific circumstances.

Global warming and other environmental concerns drive the search for alternative fuels in international shipping. A life-cycle analysis (LCA) can be utilized to assess the environmental impact of different fuels, thereby enabling the identification of the most sustainable alternative among the candidate fuels. However, most LCA studies do not consider marginal emissions, which are important when predicting the effects of large-scale fuel transitions. The research purpose of this study was to assess the marginal emissions of several currently available marine fuels to facilitate the identification of the most promising marine fuel. Thus, marginal and average emissions for eight marine fuels (high-sulfur fuel oil, very-low-sulfur fuel oil, marine gas oil, liquified natural gas, biomethane, biomethanol, fossil methanol, and hydro-treated vegetable oil) were compared in terms of their environmental impact. Non-intuitively, the results indicate that biofuels exhibit equally or higher marginal greenhouse gas emissions than conventionally used fuel oils (162–270 versus 148–174 kg CO2/MJ propulsion), despite their significantly lower average emissions (19–73 vs. 169–175 kg CO2/MJ). This discrepancy is attributed to the current limited availability of climate-efficient biofuels. Consequently, a large-scale shift to biofuels cannot presently yield substantial reductions in the shipping industry’s climate impact. Additional measures, such as optimized trading routes, more energy-efficient ships, and research on more climate-friendly biofuels and electro-fuels, are thus required to significantly reduce the climate footprint of shipping.

Bioenergy has the potential to substitute the current demand for fossil fuels in various applications. Recovering energy from bio-based materials due to environmental considerations has been adopted as a policy objective by governments and international organizations, which led to both vast financial investment and scientific research, especially in the last two decades. So far, various feedstocks and technologies have been scrutinised by the research community, although not all of them are commercially adopted due to sustainability considerations. This study employs scientometric analysis to survey the progress of scientific development in the field of bioenergy from 1966 to 2022, using ten parameters including publication year, type of document, categories, countries, affiliations, document citations, co-authorship, author citation networks, journal citation networks, and keywords. A total of 51,905 scientific documents were collected from the Web of Science, involving more than 96,000 authors from 162 countries. The dispersion of studies followed an ascending distribution with a sharp increase in the second half of the 2000s. The evolution of keywords in terms of burst strength confirmed the advancements of technologies from primary first-generation to advanced fourth-generation bioenergies. Based on the evolution of science in this area, it is concluded that integrated sustainability assessment studies, covering technical, economical, environmental, and social aspects, are needed to bridge the gap between abundant theoretical endeavours and limited commercial use of this energy source.

This study aims to assess the impact of global warming on winter wheat cultivation under different rotation systems with potato, maize or oilseed rape over a six-year period in the region of Galicia, Spain, to identify the rotation system most favorable from a climate change perspective. An attributional life cycle assessment (ALCA) with economic allocation (retrospective assessment of impacts) and a consequential life cycle assessment (CLCA) with system expansion (impacts of a change) were performed to identify discrepancies and differences in the results in this impact category and thus in the decision supported by the farmers, whose main goal is to produce wheat grain for bread purposes with the lowest carbon footprint. The global warming results modelled with ALCA and CLCA can be contradictory. In general, the climate change impact was considerably higher when modelled with CLCA than with ALCA. Farming activities were consistently identified as hotspots when using both CLCA and ALCA, but other hotspots differed in terms of their contributions. Concerning the ranking of cropping systems that produce grain with the lowest greenhouse gases emission levels, contradictory results were identified in some cases between the LCA modelling approaches. Nevertheless, the cultivation of native winter wheat under ecological management is always the preferred choice, regardless of the approach. However, wheat rotation with potato is preferrable in the ALCA, and with maize in the CLCA. The assumptions required to perform a CLCA have a large impact on results. The allocation of burdens between the co-products in the ALCA involves a level of uncertainty since discrepancies arise with the selection of the allocation procedure. Thus, the assumptions made affect the results considerably and have a direct effect on the final conclusions.

Life cycle assessment (LCA) has been recognised as an important environmental systems analysis tool due to its potential for providing systematic results about the environmental impacts of alternative production and consumption systems that can lead to decisions towards greater sustainability in both private and public-policy contexts. However, LCA has been under increased scrutiny due to the wide range of published results on similar systems, such as biofuels, which can be contrasting. This variability is, in part, due to the proliferation of guidelines that have emerged over the last 20 years, which may undermine the perceived robustness of LCA as a decision-support tool. Following some interesting discussions on this topic in different fora, we took the pulse of the LCA community via a survey. We received 124 responses from respondents who varied in their background and experience in LCA (most were academics and/or had more than 10 years' experience), as well as in their opinions on whether they saw the inconsistency of published results problematic, or not, for decision making. Results suggest that respondents are of the opinion that (i) there is no single right way of performing LCA; (ii) the ISO 14040-44 standards were failing in their guiding of LCA practice, and that (iii) further efforts in harmonizing LCA practice would be beneficial, despite mixed opinions shown by respondents, which indicates the divisive nature of this topic in the LCA community. For example, there was no clear agreement on whether the significant flexibility with which practitioners perform LCA undermines its validity as a robust tool for decision making, though practitioners concerned with greenwashing were unified in the need for improved guidelines and harmonisation. Further harmonisation would help to ensure consistency in the application of the tool by practitioners which, in turn, would ensure results would be less variable, arguably more meaningful, and less prone to greenwashing. It is likely that methodological issues will remain unresolved in the near future, as some practitioners value the flexibility with which the ISO standards can be applied, even if that leads to inconsistent results. We recommended tighter standardization.