Carbon, energy and water footprints analysis of rapeseed oil production: A case study in China

Effect of radio frequency pretreatment on the component of rapeseed and its product: Comparative study with microwave pretreatment under different oil extraction methods

Radio frequency (RF) is an emerging technology for rapeseed pretreatment, offering a comparison to the established microwave (MW) technique. This study investigated the effects of RF and MW pretreatment combined with different oil extraction methods on the oil yield, quality characteristics and lipid concomitant contents of rapeseed and its products. Results indicated that RF combined with pressing extraction yielded the highest tocopherol and canolol contents in rapeseed oil (839.6 and 1316.4 mg/kg, 8.0 % and 7.9 times higher than the control, respectively), and MW combined with supercritical carbon dioxide fluid extraction yielded the highest phytosterol content (8402.0 mg/kg, 16.6 % higher than the control). These results indicate the effectiveness of RF as a novel pretreatment method for rapeseed and its potentially greater advantage than MW. Results also imply that RF could contribute to sustainable and efficient oil extraction processes in the future food industry owing to its high efficiency and energy-saving capability.

Improving rapeseed carbon footprint evaluation via the integration of remote sensing technology into an LCA approach

Agricultural carbon footprint (CF) evaluation plays an important role in climate change mitigation and national food security. Many studies have been conducted worldwide to evaluate the CF of rapeseed and its byproducts; however, only a few of these studies have considered finer-scale spatial-temporal heterogeneity. Considering the advantages of using detailed crop information extracted by remote sensing (RS) techniques, we attempted to integrate RS into life cycle assessments to improve rapeseed CF evaluation. A case study was conducted from 2021 to 2023 in one of the most important grain- and rapeseed-producing areas in Southwest China, namely, the Chengdu Plain, covering an area of 18,810.00 km2. The results of our study suggest that: (1) the proposed approach is applicable for high-resolution (10 m ∗ 10 m) rapeseed distribution mapping; (2) the farm-based CFs of rapeseed in the studied region range from 3333.08 to 4572.82 kgCO2-eq ha-1, while the product-based CFs (PCFs) vary from 1316.23 to 2443.95 kgCO2-eq t-1. Nitrogen fertilizer processing and its application are identified as the dominant contributors to upstream and downstream greenhouse emissions (GHGs), respectively; (3) the significant role of soil properties and soil organic carbon in influencing crop PCFs indicates good GHG offsets. The method used in the current study has strong adaptability and universality in different areas with various climatic conditions and can provide a solid basis for policymakers to formulate differentiated agricultural carbon reduction policies.

Comprehensive carbon footprint analysis of wastewater treatment: A case study of modified cyclic activated sludge technology for low carbon source urban wastewater treatment

To reduce pollution and carbon emissions, a quantitative evaluation of the carbon footprint of the wastewater treatment processes is crucial. However, micro carbon element flow analysis is rarely focused considering treatment efficiency of different technology. In this research, a comprehensive carbon footprint analysis is established under the micro carbon element flow analysis and macro carbon footprint analysis based on life cycle assessment (LCA). Three wastewater treatment processes (i.e., anaerobic anoxic oxic, A2O; cyclic activated sludge technology, CAST; modified cyclic activated sludge technology, M-CAST) for low carbon source urban wastewater are selected. The micro key element flow analysis illustrated that carbon source mainly flows to the assimilation function to promote microorganism growth. The carbon footprint analysis illustrated that M-CAST as the optimal wastewater treatment process had the lowest global warming potential (GWP). The key to reduce carbon emissions is to limit electricity consumption in wastewater treatment processes. Under the comprehensive carbon footprint analysis, M-CAST has the lowest environmental impact with low carbon emissions. The sensitivity analysis results revealed that biotreatment section variables considerably reduced the environmental impact on the LCA and the GWP, followed by the sludge disposal section. With this research, the optimization scheme can guide wastewater treatment plants to optimize relevant treatment sections and reduce pollution and carbon emissions.

Life cycle assessment for evaluation of novel solvents and technologies: A case study of flavonoids extraction from Ginkgo biloba leaves

Innovative solvents such as deep eutectic solvents (DESs) and process intensification technologies assisted by ultrasound have been demonstrated to be promising pathways for enhancing solid-liquid extraction. Nevertheless, quantitative and systematic knowledge of their environmental impact is still limited. In this work, a case study of flavonoids extraction from Ginkgo biloba leaves was evaluated by using life cycle assessment (LCA) for comparison of three extraction scenarios. The first used DES as extractant (DESE), and the other two adopted ethanol, including heat reflux extraction (HRE), and ultrasound-assisted extraction (UAE). Among eight key midpoints investigated, all these from UAE were 10.0 %-80.0 % lower than from DESE and HRE except water consumption. The UAE was the eco-friendliest option due to its higher extraction yield, shorter duration and lower solvent consumption. The DESE exhibited the lowest water consumption, the highest freshwater ecotoxicity and human carcinogenic toxicity, while HRE had the highest impacts for the other 6 midpoints. Moreover, solvent production was the key contributor for all the categories. The standardized sensitivity analysis showed that the overall environmental footprint can be further decreased by 15.4 % for DESE pathways via substituting choline chloride/glycerine with choline chloride/ethylene glycol. Furthermore, all pathways using DESs had higher standardized impacts than those employing ethanol from sugarcane or wood. Replacing ethanol from maize with other feedstocks can significantly lessen the overall impacts, among which the UAE using ethanol from sugarcane demonstrated the least environmental impacts. The promotion of DESs as "green and sustainable" alternative to traditional solvents requires careful consideration.

Identifying synergistic solutions for the food-energy-water nexus via plastic film mulching cultivation

Food security, water scarcity, and excessive fossil energy use pose considerable challenges to sustainable agriculture. To understand how rain-fed farming systems on the Loess Plateau, China, reconcile yield increases with ecological conservation, we conducted an integrated evaluation based on the denitrification-decomposition (DNDC) model, agricultural statistics data using the Food-Energy-Water (FEW) nexus indicator. The results showed that maize yields with ridge-furrow plastic film mulching (PFM) were 3479, 8942, and 11,124 kg ha-1 under low (50 kg N ha-1), medium (200 kg N ha-1), and high (350 kg N ha-1) nitrogen (N) fertilizer rates, respectively, and that PFM increased yield and water use efficiency (WUE) by 110-253 % and 166-205 % compared to using no mulching (control, CK), respectively. Plastic film mulching also increased net energy (126-436 %), energy use efficiency (81-578 %), energy productivity (100-670 %), and energy profitability (126-994 %), and nitrogen fertilizer, compound fertilizer, and diesel fuel consumption by agricultural machinery were the main energy inputs. The PFM system reduced water consumption during the maize growing season and the green water footprint and gray water footprint decreased by 66-74 % and 44-68 %, respectively. The FEW nexus indicator, based on a high production at low environmental cost scenario, was greater under the PFM system and had the widest spatial distribution area at the medium-N application rate. Among the environmental factors, the nexus indicator was negatively correlated with precipitation (-0.37), air temperature (-0.36), and the aridity index (-0.36), but positively correlated with elevation (0.17). Our results suggest that the PFM system promotes resource-saving while increasing yields and moves dryland agriculture in an environmentally friendly direction, thus promoting the sustainable development of agroecosystems.

Uncovering the energy-carbon-water footprint of waste rubber recycling: Integrated environmental and economic perspectives

The commitment to waste management has gained increasing momentum as global waste generation continues to skyrocket and threaten the environment. However, detailed assessments and clear insights remain absent to address the global waste utilization conundrum. This study evaluated the impact-oriented energy, carbon, and water (ECW) footprints of three typical scenarios for a waste recycling activity (i.e., waste rubber recycling) from environmental and economic dimensions, and explored key factors, nexus characteristics, and optimization measures. Results indicated that the rubber powder as an asphalt modifier scenario had a 93% greater environmental impact and 87% higher economic cost compared with the pyrolysis and reclaimed rubber production scenarios. Key processes, such as direct processes, electricity generation, and transportation, were identified as the major contributors to the ECW footprints, with the internal costs of raw materials, equipment, and taxes coupled with the external costs of human health dominating the economic impact. The nexus analysis results highlighted the urgent need to optimize the energy system for waste rubber recycling. Greening the production process revealed the benefits, with natural additives mitigating 85% of the environmental burden and 97% of the external costs compared with conventional additives. Industrial green microgrids, clean energy generation, proximity waste management, and electrified transportation were explored to foster sustainable optimization of waste rubber recycling systems. Moreover, a joint tax-subsidy mechanism for rubber production-recycling systems can stimulate recycling-oriented product design and increase the motivation to recycle waste rubber.

Detection of lead content in oilseed rape leaves and roots based on deep transfer learning and hyperspectral imaging technology

The evaluation capability of hyperspectral imaging technology was studied for the forecasts of heavy metal lead concentration of oilseed rape plant. In addition, a transfer stacked auto-encoder (T-SAE) algorithm including two network methods, the dual-model T-SAE and the single-model T-SAE, was proposed in this paper. The hyperspectral images of oilseed rape leaf and root were acquired under different Pb stress concentrations. The entire region of the oilseed rape leaf (or root) was selected as the region of interest (ROI) to extract the spectral data, and standard normalized variable (SNV), first derivative (1st Der) and second derivative (2nd Der) were used to preprocess the ROI spectra. Besides, the principal component analysis (PCA) algorithm was used to reduce the dimensionality of the spectral data before and after preprocessing. Hence, the best pre-processed data was determined for subsequent research and analysis. Furthermore, the SAE deep learning networks were built based on the oilseed rape leaf data, oilseed rape root data, and the combined data of oilseed rape leaf and root based on the best pre-processed spectral data. Finally, the T-SAE models were obtained through transfer learning of the best SAE deep learning network. The results show that the best preprocessing algorithms of the oilseed rape leaf and root spectra were SNV and 1st Der algorithm, respectively. In addition, the prediction set recognition accuracy of the best T-SAE model of Pb stress gradient in oilseed rape plants was 98.75%. Additionally, the prediction set coefficient of determination of the best T-SAE model of the Pb content in the oilseed rape leaf and root data were 0.9215 and 0.9349, respectively. Therefore, a deep transfer learning method combined with hyperspectral imaging technology can effectively realize the the qualitative and quantitative detection of heavy metal Pb in oilseed rape plants.

Effect of Different Extraction Methods on Quality Characteristics of Rapeseed and Flaxseed Oils

This study reports the effect of roasted pretreatment combined with screw press, hydraulic press, and Soxhlet extraction methods on various quality indexes of rapeseed and flaxseed oils, including the oil yield, sensory indexes (color, smell, clarity, viscosity, and colligation score), physicochemical properties (acid value, peroxide value, saponification value, moisture and volatiles), major components (fatty acid composition and triglyceride composition), and minor components (volatile compounds, total phenols, and vitamin E contents). The results indicated that the oil yield, sensory indexes, physicochemical properties, fatty acid composition, volatile compounds, total phenol, and vitamin E contents in vegetable oils have been significantly affected by different extraction methods. The yields of rapeseed and flaxseed oils of Soxhlet extraction method were increased by 30.10%–73.90% and 6.30%–54.40%, respectively, compared with other treatment groups. In addition, roasted pretreatment significantly increased the yields of oils by 4.10%–25.00% and 6.70%–23.15%, respectively, compared with the untreated group. The contents of linolenic acid and vitamin E in rapeseed and flaxseed oils extracted from screw press method were higher. In particular, the linolenic acid content of cold-pressed rapeseed oil extracted by screw press increased by 1.50%–23.80% compared with other treatment groups. In addition, the contents of vitamin E in cold-pressed rapeseed oil and flaxseed oil obtained by screw press increased by 1.22%–78.91% and 3.00%–18.80%, respectively. The Soxhlet extraction could improve oil yield and total phenol content, but the quality of the oil was inferior due to high acid values (0.93–3.36 mg KOH/g) and peroxide values (0.70–5.23 meq O2/kg). Furthermore, the hydraulic press method could extract vegetable oils with excellent sensory scores. The roasted pretreatment gives the rapeseed and flaxseed oils a good smell. The major volatile compounds in rapeseed and flaxseed oils were aldehydes, acids, alcohols, heterocycles, and ketones. Different extraction methods and pretreatment had no significant effect on the compositions and contents of triglycerides. This study provides a basic understanding on the selection of appropriate oil extraction techniques for oil extraction at a large scale.