Impact of lowered vehicle weight of electric autonomous tractors in a systems perspective

Modern agriculture rely on heavy machinery that has increased risk of detrimental soil compaction of arable fields. This can lead to negative effects such as reduced yields, reduced field trafficability and increased fuel use. Electric, autonomous tractors makes it possible to replace one heavy machine with several lighter without increased labour costs. In this study, the economic and environmental effects of reduced soil compaction for smaller autonomous tractors were assessed and compared to a scenario with conventional tractors. A discrete event simulation of a Swedish 200 ha grain farm with clay soil was used for the calculations. The electric, autonomous system had lower soil compaction impacts as well as other benefits, and reduced cost in total from 385 to 258 euro ha-1 and the climate impact from 270 to 77 kg CO2eq ha-1 compared to the conventional scenario. Soil compaction constituted 20% of the cost and 26% of the climate impact for the conventional scenario. It was concluded that soil compaction was impactful in machinery studies, especially on heavier soil like clay, and should not be omitted. Soil compaction avoidance alone was not impactful enough to warrant a change to electric, autonomous tractors but it reinforced already existing trends and further improved the cost and environmental benefits

Arbetsmaskiners bidrag till luftföroreningar i tätorter

The Swedish government has decided an action plan against particulate matter (PM10) within the county of Stockholm. Among other thing, the action plan stipulate that measures shall be taken in order to increase the knowledge about emissions of PM10 from non-road mobile machinery and their contribution to the air quality within densely populated areas. Non-road mobile machinery are characterised as mobile machinery not intended for the use of passenger- or goods-transport on the road, and equipped with an internal combustion engine as specified in directive 97/68/EC and directive 2000/25/EC, i.e. agricultural and forestry tractors and construction equipment such as wheel loaders, excavators, articulated haulers and mobile cranes. The purpose of this project, which was financed by the Swedish national road administration, was to update and summarise the current knowledge concerning fuel consumption and emissions from non-road mobile machinery and their contribution to the air quality in densely populated areas. A more specific aim of the project was to estimate the occurrence and age distribution and annual work hours of non-road mobile machinery within densely populated areas. Furthermore, annual fuel consumption and emissions amounts were also derived. Usually a single emission factor for each pollutant has been used when estimating emissions from the entire non-road mobile machinery sector, which has resulted in fairly uncertain results. Previous research has shown that it is not possible to develop one single set of emission factors that gives representative results for all types of non-road mobile machinery and operations (Hansson et al., 2001; Starr et al., 1999; Ullman et al., 1999). The latest research within the EMMA-projects in Sweden about the presence, use and emissions from non-road mobile machinery has resulted in better knowledge and data concerning emissions from non-road mobile machinery. Within the present project, emissions from non-road mobile machinery in two densely populated areas or population centres with different sizes have been studied. One large population centre represented by the city of Stockholm and one small represented by the town of Ljungby. The calculation of fuel consumption and emissions from non-road mobile machinery within the city of Stockholm has been conducted in accordance with the advanced approach presented by the emission inventory guidebook from the European Environement Agency (EEA, 2005). However, the methodology has been modified in order to thoroughly represent the actual assembly of non-road mobile machinery including the work performed by those machines annually. The same model that was used to derive fuel consumption has been employed for emissions as well. Compared with using average information, more reliable data were obtained through describing the number of machines, annual hour, engine power, load factor, specific fuel consumption and emissions amounts for each type of non-road mobile machinery and model year. All data were stored and used in different matrices, one for each variable. In total 31 different types of machines were defined for which data were collected for all model years from 1982 to 2006. Extensive inventories of non-road mobile machinery were carried out for both the city of Stockholm and Ljungby. For Stockholm the inventory contained both number of units and annual work hour as function of the age of the machinery. Reliable data could be obtained through the Swedish Machinery Testing Institute’s accredited inspection database in combination with statistics over both annual sale returns and registered machinery from the national vehicle database. The results from the inventory showed that about 2 800 non-road mobile machinery with both varying age and annual work hours operated within the city of Stockholm. In the city of Ljungby, less than 100 non-road mobile machinery were estimated to operate, thus called for an alternative method for the inventory. Based on data from local contractors that operated in the city of Ljungby, annual work hour for different types of non-road mobile machinery were collected. The result showed that about 48 000 hours of work with non-road mobile machinery were carried out within the city of Ljungby annually. Moreover, the majority of the work were performed with wheel loaders and different types of excavators. In table S1 annual emission- and fuel consumption amounts from the non-road mobile machinery sector in the cities of Stockholm and Ljungby year 2006 are shown

Time-dependent climate impact of beef production - can carbon sequestration in soil offset enteric methane emissions?

The time-dependent climate impact of beef production, including changes in soil organic carbon, was examined in this study. A hypothetical suckler cow system located in south-east Sweden was analysed using a time dependent life cycle assessment method in which yearly fluxes of greenhouse gases were considered and the climate impact in terms of temperature response over time was calculated. The climate impact expressed as carbon dioxide equivalents, i.e. global warming potential in a 100-year time perspective, was also calculated. The Introductory Carbon Balance Model was used for modelling yearly soil organic carbon changes from land use. The results showed an average carbon sequestration rate of 0.2 Mg C ha(-1) and yr(-1), so carbon sequestration could potentially counteract 15-22% of emissions arising from beef production (enteric fermentation, feed production and manure management), depending on system boundaries and production intensity. The temperature response, which showed a high initial increase due to methane emissions from enteric fermentation, started to level off after around 50 years due to the short atmospheric lifetime of methane. However, sustained production and associated methane emissions would maintain the temperature response and contribute to climate damage. A forage-grain beef system resulted in a lower climate impact than a forage-only beef system (due to higher slaughter age), even though more carbon was sequestered in the forage-only system

Performance comparison of charging systems for autonomous electric field tractors using dynamic simulation

A model simulating an autonomous battery electric vehicle system for agricultural field use was created, assuming a 200-ha conventional cereal farm in Swedish conditions. The different subsystems were verified against sources in the literature, field experiments and general common practice. The model was used to compare two different charging systems (conductive charging and battery exchange) for battery electric tractors to each other. A comparative simulation was made with conventional diesel systems (fully autonomous or manned for 10 h d(-1)). The simulation results indicated that battery exchange was generally a faster system than conductive charging. The results also showed that both electric systems were able to achieve similar active time during spring field operations as a corresponding system of a simulated manned diesel tractor for battery sizes from 50 kWh and charge powers from 50 kW. (C) 2020 The Authors. Published by Elsevier Ltd on behalf of IAgrE

Climate impact of willow grown for bioenergy in Sweden

Short-rotation coppice willow (SRCW) is a fast-growing and potentially high-yielding energy crop. Transition to bioenergy has been identified in Sweden as one strategy to mitigate climate change and decrease the current dependency on fossil fuel. In this study, life cycle assessment was used to evaluate and compare the climate impacts of SRCW systems, for the purpose of evaluating key factors influencing the climate change mitigation potential of SRCW grown on agricultural land in Sweden. Seven different scenarios were defined and analysed to identify the factors with the most influence on the climate. A carbon balance model was used to model carbon fluxes between soil, biomass and atmosphere under Swedish growing conditions. The results indicated that SRCW can act as a temporary carbon sink and therefore has a mitigating effect on climate change. The most important factor in obtaining a high climate change-mitigating effect was shown to be high yield. Low yield gave the worst mitigating effect of the seven scenarios, but it was still better than the effect of the reference systems, district heating produced from coal or natural gas

Albedo on cropland: Field-scale effects of current agricultural practices in Northern Europe

Agricultural land use and management affect land surface albedo and thus the climate. Increasing the albedo of cropland could enhance reflection of solar radiation, counteracting the radiative forcing (RF) of greenhouse gases (GHGs) and local warming. However, knowledge is lacking on how agricultural practices affect albedo under local conditions, and on the benefits of individual practices. In this study, field measurements were made in 15 paired plots at a site in Northern Europe to determine albedo, net shortwave irradiance and RF impacts under various common crops, cultivation intensities and tillage practices. Field data for 2019-2020 were compared with satellite-based albedo for the surrounding region in 2010-2020. At regional level, different combinations of soil type, yearly weather and agricultural practices led to great variability in the albedo of individual crops, despite similar pedo-climatic conditions. At field level within years, albedo differences were determined mainly by crop type, species-specific phenology and post-harvest management. Annual albedo was higher with perennial ley (0.20-0.22) and winter-sown crops (0.18-0.22) than with spring-sown crops (0.16-0.18) and bare soil (0.13). Barley had the highest albedo among winter and spring cereals. In summer, when increased albedo could alleviate local heat stress, oats reduced net shortwave irradiance at the surface by 0.8-5.8 Wm(-2) compared with other cereals, ley, peas or rapeseed. Delayed or reduced tillage gave high local cooling potential (up to-13.6 Wm(-2)) in late summer. Potential benefits for global mean climate as GWP(100 )per hectare and year reached-980 kg CO(2)e for avoiding black fallow,-578 kg CO(2)e for growing a winter-sown variety and-288 kg CO(2)e for delayed tillage. Thus realistic albedo increases on cropland could have important effects on local temperatures and offset a substantial proportion of the RF deriving from field-scale GHG emissions on short time-scales

Regional variation in climate impact of grass-based biogas production: A Swedish case study

Transitioning from a fossil economy to a bio-economy will inevitably increase the demand for biomass production. One strategy to meet the demand is to re-cultivate set-aside arable land. This study investigated the climate impact and energy potential of grass-based biogas produced using fallow land in Uppsala municipality, Sweden. The assessment was performed on regional level for more than 1000 individual sites, using the agro-ecosystem model DeNitrification DeComposition (DNDC) in combination with time-dynamic life cycle assessment methodology. The results showed that the system could significantly increase biogas production within the region, which would reduce the climate impact by 9950 Mg CO2-eq per year. Compared with diesel fuel, the grass-based biogas gave a GWP reduction of 85%. However, the site-specific GWP reduction showed large spatial variability, ranging between 102 and 79% compared with diesel fuel, depending on where in the region the grass was cultivated. Two alternative scenarios were investigated, increased mineral N fertilisation and inclusion of N-fixing crops in the feedstock mixture. The highest mitigation per biogas energy produced was found for the N-fixing scenario but, because of lower yields, this scenario had lower total mitigation potential for the region than the increased fertilisation scenario. The increased fertilisation scenario had a lower climate mitigation effect per biogas energy produced, but the highest mitigation potential when the whole region was considered, because of the increased biogas production. The method applied in this study can guide land-use planning of local energy production from arable land, also for other regions. (C) 2020 The Author(s). Published by Elsevier Ltd

Albedo impacts of current agricultural land use: Crop-specific albedo from MODIS data and inclusion in LCA of crop production

Agricultural land use and management practices affect the global climate due to greenhouse gas (GHG) fluxes and changes in land surface properties. Increased albedo has the potential to counteract the radiative forcing and warming effect of emitted GHGs. Thus considering albedo could be important to evaluate and improve agricultural systems in light of climate change, but the albedo of individual practices is usually not known. This study quantified the albedo of individual crops under regional conditions, and evaluated the importance of albedo change for the climate impact of current crop production using life cycle assessment (LCA). Seven major crops in southern Sweden were assessed relative to a land reference without cultivation, represented by semi-natural grassland. Crop-specific albedo data were obtained from a MODIS product (MCD43A1 v6), by combining its spatial response pattern with geodata on agricultural land use 2011–2020. Fluxes of GHGs were estimated using regional data and models, including production of inputs, field operations, and soil nitrogen and carbon balances. Ten-year mean albedo was 6–11% higher under the different crops than under the reference. Crop-specific albedo varied between years due to weather fluctuations, but differences between crops were largely consistent. Increased albedo countered the GHG impact from production of inputs and field operations by 17–47% measured in GWP100, and the total climate impact was warming. Using a time-dependent metric, all crops had a net cooling impact on global mean surface temperature on shorter timescales due to albedo (3–12 years under different crops), but a net warming impact on longer timescales due to GHG emissions. The methods and data presented in this study could support increasingly comprehensive assessments of agricultural systems. Further research is needed to integrate climatic effects of land use on different spatial and temporal scales, and direct and indirect consequences from a systems perspective

Climate effects of a forestry company : including biogenic carbon fluxes and substitution effects

Forestry will play an important role in a future bioeconomy, by providing wood fibres for biomaterial and bioenergy. However, there are contradictory opinions on the climate change mitigation potential of forestry. Stora Enso, an international forestry company, has the ambition to improve its climate impact assessment at corporate level. In this work, a system perspective was applied, where greenhouse gas emissions from value chains, biogenic carbon fluxes from forest land owned or leased by Stora Enso and temporarily stored in harvested wood products, and the substitution effect, i.e. avoided emissions from substituted products and energy were considered. Furthermore, new substitution factors for pulp and paper products were developed. The estimated climate effect at corporate level was a net removal of -11.5 million Mg CO2-eq yr-1 (i.e. a climate benefit) when considering value chain emissions, biogenic carbon fluxes from forest land and harvested wood products, and avoided emissions from substitution. Uptake of biogenic carbon counteracted around 40% of the value chain emissions, while the largest climate benefit (removal of 17.9 million Mg CO2-eq) was due to substitution of more greenhouse gas-intensive products. The new substitution factors developed for pulp and paper products were applied in the climate impact calculation at company level. Important assumptions and possible improvements for future studies were identified, e.g. how to assess the impact of cascading wood use in substitution calculations

Future climate impacts of sodium-ion batteries

Sodium-ion batteries (SIBs) have emerged as an alternative to lithium-ion batteries (LIBs) due to their promising performance in terms of battery cycle lifetime, safety, operating in wider temperature range, as well as the abundant and low-cost of sodium resources. This study evaluated the climate impacts of three SIBs, and compared to two LIBs under four scenarios with considering potential changes in battery performance and background productions between 2020 and 2050. To ensure a fair comparison, all batteries were modeled in the 21,700 form, and a battery dimensioning model was developed to calculate the required amount of components for each battery. We found that equal to lower GHG emissions result from the use of SIBs compared to LIBs under optimal performance scenarios. From 2020 to 2050, the climate impacts of SIBs decreased by 43-57 %. The relative contribution of the battery manufacturing process decreases from 18-32 % to 2-4 % due to the increasingly share of clean energy in the electricity grid, while the relative contribution of key battery component materials increases over time, especially for cathode active materials. These results emphasize the significance of decarbonizing the electric grid, and suggest that future investment in SIBs is promising from an environmental point of view