Energy Return On Investment Research Articles

Agricultural Waste Valorization: Exploring Environmentally Friendly Approaches to Bioenergy Conversion

The pursuit of sustainable energy production through the conversion of agricultural waste into different bioenergy resources is of paramount importance given its potential to mitigate environmental impact while meeting energy demands. In this review, a comprehensive overview of the technologies for the biochemical and thermochemical conversion of agricultural waste into bioenergy is provided. A summary of the process of its conversion into different bioenergy products such as biogas, bio-oil, and biofuel is provided, in addition to the potential advantages and challenges faced using different biomass conversion technologies. The review highlights the potential of agricultural waste valorization to address the current energy demand while at the same time contributing to environmental benefits and greenhouse gas emission reductions. Moreover, this review highlights some significant gaps for improvement. These include the challenges in the pretreatment of agricultural waste biomass in optimizing the conversion rates and lowering the required energy consumption throughout the process while enhancing both the quantity and quality of the output. Some recommendations are proposed to address the identified challenges. These include the need for further studies for a thorough assessment to evaluate the efficacity and sustainability of agricultural waste valorization technologies. Assessment methods such as life cycle assessment (LCA), life cycle analysis (LCA), net energy ratio (NER) calculations, life cycle costing (LCC), as well as techno-economic assessment (TEA), are recommended, together with collaboration among governments, farmers, and researchers, as well as the integration of cutting-edge technologies to enhance various aspects of agricultural waste, optimizing the conversion process, cost efficiency, time management, and labor requirements, consequently boosting the conversion efficiency and product quality.

Harnessing Photo‐to‐Thermal Conversion in Sulfur‐Vulcanized Mxene for High‐Efficiency Solar‐to‐Carbon‐Fuel Synthesis

AbstractHarnessing solar energy for the conversion of CO2 into value‐added chemicals and fuels represents a promising strategy for sustainable development. Photo‐to‐thermal (PTT) conversion, an often‐underestimated factor, offers a remarkable approach to enhance the photocatalytic transformation of CO2, by reducing the activation energy of catalytic reactions and accelerating reaction kinetics. In order to achieve a higher energy return on investment (EROI), in this study, a sulfur‐vulcanized, multi‐layer Ti3C2 MXene is unveiled, capable of efficient sunlight‐driven CO2 photoreduction, by capitalizing on PTT conversion across the full visible‐to‐near‐infrared (NIR) spectrum. The vulcanization strategy is pivotal here, as it not only introduces an abundance of reactive sites but also extends the NIR response (peaking at 1095 nm) of MXene. The resulting rapid PTT and synergistic photo‐thermal‐catalytic CO2 reduction constitute a significant advance in this area, where CH4 (12.03 mmol g−1 h−1) and C2H4 (3.55 mmol g−1 h−1) yields are achieved with a C2+ selectivity of 29.76% under concentrated natural sunlight. This work sets a new benchmark for EROI with an average solar‐to‐carbon‐fuel (STF) conversion efficiency greater than 0.045%.

Research on Life Cycle Assessment and Performance Comparison of Bioethanol Production from Various Biomass Feedstocks

Bioethanol, as a renewable energy source, has been widely used in the energy sector, particularly in replacing traditional petroleum energy, and holds great potential. This study involves a whole life cycle assessment of bioethanol production and the co-production of high-value by-products—xylose, lignin, and steam—using three types of waste biomass: corn cobs, corn straw, and wheat straw as feedstocks by chopping, pretreatment, hydrolysis, fermentation, and distillation methods. Secondly, the benefits of three raw materials are compared for preparing bioethanol, and their impact on the environment and energy production is analyzed. The comparison indicates that corn cobs offer the best overall benefits, with a net energy balance (NEB) of 6902 MJ/Mg of ethanol and a net energy ratio (NER) of 1.30. The global warming potential (GWP) is 1.75 × 10−2, acidification potential (AP) is 1.02 × 10−2, eutrophication potential (EP) is 2.63 × 10−4, photochemical ozone creation potential (POCP) is 3.19 × 10−8, and human toxicity potential (HTP) is 1.52 × 10−4. This paper can provide a theoretical reference and data supporting the green refining of bioethanol and the high-value utilization of by-products, and broaden its application prospects.

Life-cycle and economic assessments of microalgae biogas production in suspension and biofilm cultivation systems

Biogas production via anaerobic digestion is highly attractive for microalgae. The technology of microalgae cultivation has profound impacts on biogas production system as it is the most energy-consuming process. However, a comprehensive evaluation of the environmental and economic benefits of different cultivation systems has yet to be sufficiently conducted. Here, life-cycle and economic assessments of open raceway ponds, photobioreactors and biofilm systems were investigated. Results showed greenhouse gas emissions of all systems were positive because more than two-thirds of carbon in fuel gas was lost and the fixed carbon in product gas and solid fertilizer was less than the emitted carbon during energy input. Particularly, biofilm system achieved the least greenhouse gas emissions (9.3 g CO2-eq/MJ), net energy ratio (0.7) and levelized cost of energy (0.9 $/kWh), indicating the optimum cultivation system. Open raceway ponds and photobioreactors failed to achieve positive benefits because of low harvesting efficiency and biomass concentration.

Systemwide energy return on investment in a sustainable transition towards net zero power systems

The Glasgow Climate Pact articulated the vital importance of renewables in reducing emissions on the way to net-zero pledges. During the power sector transition, foreseeing conditions affecting the plausibility of pathway options is crucial for specifying an optimal system development strategy. This study examines the net energy performance of nine decarbonisation global energy transition scenarios until 2050 by applying a newly developed systemwide energy return on investment (EROI) model. All scenarios result in an EROI value above the upper limit of the net energy cliff, expected to be around 10. EROI trends heavily depend on transition paths. Once achieving higher renewable energy shares begin requiring significant enabling technologies, EROI continually declines as the shares increase. Shortening the transition period leads to a sharper declining of EROI, which stabilises after achieving 100% renewables. The vulnerability arising from natural gas and oil depletions may have worst impact on EROI of fossil fuels dominated systems.

Life cycle assessment of integrated microalgae oil production in Bojongsoang Wastewater Treatment Plant, Indonesia.

This study aims to determine the eco-friendliness of microalgae-based renewable energy production in several scenarios based on life cycle assessment (LCA). The LCA provides critical data for sustainable decision-making and energy requirement analysis, including net energy ratio (NER) and cumulative energy demand (CED). The Centrum voor Milieuwetenschappen Leiden (CML) IA-Baseline was used on environmental impact assessment method by SimaPro v9.3.0.3® software and energy analysis of biofuel production using native polyculture microalgae biomass in municipal wastewater treatment plants (WWTP) Bojongsoang, Bandung, Indonesia. The study was analyzed under three scenarios: (1) the current scenario; (2) the algae scenario without waste heat and carbon dioxide (CO2); and (3) the algae scenario with waste heat and carbon dioxide (CO2). Waste heat and CO2 were obtained from an industrial zone near the WWTP. The results disclosed that the microalgae scenario with waste heat and CO2 utilization is the most promising scenario with the lowest environmental impact (- 0.139kg CO2eq/MJ), positive energy balance of 1.23MJ/m3 wastewater (NER > 1), and lower CED value across various impact categories. It indicates that utilizing the waste heat and CO2 has a positive impact on energy efficiency. Based on the environmental impact, NER and CED values, this study suggests that the microalgae scenario with waste heat and CO2 is more feasible and sustainable to adopt and could be implemented at the Bojongsoang WWTP.

Comparing the net-energy balance of standalone photovoltaic-coupled electrolysis and photoelectrochemical hydrogen production.

Photovoltaic-coupled electrolysis (PV-E) and photoelectrochemical (PEC) water splitting are two options for storing solar energy as hydrogen. Understanding the requirements for achieving a positive energy balance over the lifetime of facilities using these technologies is important for ensuring sustainability. While neither technology has yet reached full commercialisation, they are also at very different technology readiness levels and scales of development. Here, we model the energy balance of standalone large-scale facilities to evaluate their energy return on energy invested (ERoEI) over time and energy payback time (EPBT). We find that for average input parameters based on present commercialised modules, a PV-E facility shows an EPBT of 6.2 years and ERoEI after 20 years of 2.1, which rises to approximately 3.7 with an EPBT of 2.7 years for favourable parameters using the best metrics amongst large-scale modules. The energy balance of PV-E facilities is influenced most strongly by the upfront embodied energy costs of the photovoltaic component. In contrast, the simulated ERoEI for a PEC facility made with earth abundant materials only peaks at 0.42 after 11 years and about 0.71 after 20 years for facilities with higher-performance active materials. Doubling the conversion efficiency to 10% and halving the degradation rate to 2% for a 10-year device lifetime can allow PEC facilities to achieve an ERoEI after 20 years of 2.1 for optimistic future parameters. We also estimate that recycling the materials used in hydrogen production technologies improves the energy balance by 28% and 14% for favourable-case PV-E and PEC water splitting facilities, respectively.

Energy Return On (energy) Invested (EROI) and its importance in assessing the performance of energy systems

Meeting the energy needs of our societies, in the context of the fight against global warming and the prospect of depleting stocks of fossil fuels and mineral resources, requires the implementation of low-carbon alternative solutions. The cost per MWh is undoubtedly a useful criterion, but physical criteria are essential for assessing technological solutions and possible energy scenarios. The main of these criteria based on physical quantities is the “Energy Return on Invested” (EROI), which measures the efficiency of a system in providing society with useful energy for sectors other than the energy sector itself. Other aspects must also be considered, such as the availability of resources, the surface areas mobilised, mineral requirements, industrial risks and environmental and health impacts.

Life-cycle assessment of microalgae liquid biofuel production in biofilm cultivation system via conversion technologies of transesterification, hydrothermal liquefaction and pyrolysis

Biofilm seems to be an ideal cultivation system for microalgae liquid biofuel conversion technologies due to the advantage of high biomass concentration. However, research on the biofilm cultivation system for microalgae liquid biofuel producing were limited. In this study, a life-cycle assessment was conducted for microalgae liquid biofuel production in this system via three conversion technologies: transesterification, hydrothermal liquefaction and pyrolysis. The result shows that scenario hydrothermal liquefaction seems to be the most feasible technology to produce liquid biofuel in biofilm system because only hydrothermal liquefaction achieved positive energy and environment benefits with a net energy ratio of 0.87 and Greenhouse gas emissions of −39.91 g CO2-eq MJ−1. For transesterification and pyrolysis, the net energy ratio (2.18 and 2.06) were larger than 1, while Greenhouse gas emissions (3.28 and 59.25 g CO2-eq) were greater than 0. This indicated that these scenarios exhibited negative energy and environment benefits due to heavy use of chemicals and high energy consumption during biomass drying process, respectively. Additionally, according to the sensitivity analysis, bio-crude mass yield exhibited a more significant impact on the energy and environment loads for scenario hydrothermal liquefaction than the other factors.

Evaluation of orally administered Megasphaera elsdenii in steer calves abruptly transitioned from a receiving diet with 4% dietary starch to a growing diet with 38% dietary starch.

The objective of this experiment was to evaluate the effects of orally administered Megasphaera elsdenii NCIMB 41125 as a microbial supplement in steers abruptly transitioned from a receiving diet with 4% dietary starch (dry matter [DM] basis) to a growing diet with 38% dietary starch (DM basis). Steers (n = 192; initial shrunk body weight [SBW] = 309 ± 20.6kg) were assigned to microbial supplement treatment in a randomized complete block design. Treatments were control (CON): no microbial supplement prior to diet transition, and (DFM): microbial supplement orally administered prior to diet transition (20mL of microbial supplement [Lactipro NXT, Axiota Animal Health, Fort Collins, CO] containing 1 × 1010 colony forming units Megasphaera elsdenii NCIMB 41125). Steers were sourced from a previously conducted 49 d feedlot receiving period experiment and abruptly transitioned from a receiving diet including soybean hulls and wheatlage containing 4% dietary starch (DM basis) to a growing diet including high-moisture ear corn, dry-rolled corn, and wheatlage containing 38% dietary starch (DM basis). Diets were switched on an equal DM intake basis to achieve the abrupt change and steers were fed the 38% starch diet for 49 d until experiment completion. Prior to experiment initiation, steers (n = 72; n = 3/pen) were fitted with wireless rumination tags to track daily activity and rumination time. No differences (P ≥ 0.20) were observed between treatments for final SBW, average daily gain, DM intake, feed efficiency, calculated net energy (NE) for maintenance and gain, or observed-to-expected ratio of NE for maintenance and gain. Additionally, no treatment × day or treatment differences (P ≥ 0.12) were observed for activity or rumination measures. Minutes ruminating and active both differed (P < 0.01) for the main effect of day. Compared to non-supplemented steers, oral administration of Megasphaera elsdenii NCIMB 41125 did not improve growth performance or efficiency of dietary NE utilization in steers transitioned from a receiving diet containing 4% starch (DM basis) to a growing diet containing 38% starch (DM basis).

Parandettevõtlus: praktiline radikalism / Regenerative entrepreneurship: practical radicalism

‘Progress’ means extravagant energy use, enabled by the burning of fossil fuels and colonial expansion. The peak in the extraction of oil and countless other key natural resources, the ‘peak everything’, is at hand or imminent. Renewable and nuclear energy depend on fossil fuel-based production and have a poor EROI (energy return on investment). At the same time, the industrial civilisation has triggered a series of irreversible chain reactions. For the last 10,000 years, a period known as the Holocene, the Earth has enjoyed an exceptionally stable climate, which is a prerequisite for agriculture and the functioning of civilisations. We are entering a hothouse Earth with an unstable climate. The author starts from a post-sustainable framework of deep adaptation, according to which the collapse of industrial societies due to climate chaos and limits to growth is likely, inevitable or already underway in our lifetime. The essential question of the post-sustainable world is how to live on a planet, on which humankind has never set foot in its entire evolution. In order to conceptualise this situation and to create an action plan, it is necessary to abandon the dogma of progressivism, the narrative that everything is going to get better, that all stories have a happy ending, and that there is no ‘going back to childhood’ (to a ‘Golden Age’, ‘traditional society’, etc.). The author takes a brief look at empirical and theoretical analyses that are in sharp contrast to the basic narratives of progress. The author also points out that no scientific-technical, Enlightenment-based culture or cultural situation in history can be shown to have been sustainable for even a single moment. At the same time, history is littered with examples of former state subjects, who have fled civilisation and gone native. Consequently, the achievement of an ecologically sustainable culture that breaks away from the doctrines of the Enlightenment and progress is an opportunity that is within reach at any moment. Since the mid-19th century (at the latest), Estonian culture has consisted of attempts to create European-style culture in Estonian. In order to reach an ecologically sustainable way of life that can be lived from generation to generation, it is necessary to search for and invent the “modes of creation” of Estonians as a countryside people (before the 19th century, Estonians called themselves “people of the land”), i.e., a local epistemology and ecological sensitivity of the local culture, rebuilding a photosynthesis-based food system. The author calls for the abandonment of modernist business as usual and for the actual care of the land, generation after generation, a regenerative economy. The task of the regenerative economy is to bind water, carbon, nutrients into the Estonian soil. Agriculture – to the extent that it is possible on a hothouse Earth – must move towards forest gardening and grazing, because carbon is better safeguarded in the soil than in vegetation in the event of wildfires and superstorms. Also, it will be harder for colonisers to seize crops. Regenerative economy can be summed up in three words: food, wood, fibre. Finally, the author proposes an extensive list of ideas for regenerative entrepreneurship. A regenerative entrepreneur is a practical environmental radical, whose everyday challenge is to find business models that are based on human or animal labour and photosynthesis as a source of energy and to create soil. Keywords: limits to growth, climate chaos, deep adaptation, going native, regenerative economics

Exploring the effects of mineral depletion on renewable energy technologies net energy returns

The energy transition poses a set of new challenges related to mineral scarcity and depletion. The process of mineral depletion is characterised by increasing energy consumption per tonne of valuable minerals mined (i.e. energy intensity of mining), due to the decline in the quality of mined deposits. As renewable energy technologies are heavily reliant on a range of minerals, some of them scarce, the net energy returns (i.e., the share of energy available to provide energy services) of renewable energy technologies may be significantly affected by this decline. This may in turn jeopardise the ability of renewable energy technologies to provide sufficient net energy, and hence, support decent living standards. The aim of this article is therefore to explore, using net energy analysis techniques combined with Life Cycle Analysis data, the effects of mineral depletion on the net energy returns of four renewable energy technologies: solar photovoltaic, concentrated solar power, onshore wind, and offshore wind.The results indicate that the effects of mineral depletion on the net energy returns of renewable energy technologies will be marginal. Indeed, even for very high increases in the energy intensities of mining, the share of net energy returns decreases by less than 3 percentage points by 2060 for each technology analysed — 2.3% for wind offshore, 1.6% for solar photovoltaic and concentrated solar power, and 1.1% for wind onshore. These results are validated with a Monte Carlo simulation conducted on the energy intensities of mining. In addition, the article discusses that technological factors, such as improvements in metallurgical energy efficiencies and material intensities of manufacturing have the potential to somewhat offset the effects of mineral depletion. Hence, although constraints related to mineral scarcity and depletion may be critical for the energy transition, concerns regarding the impacts of these issues on the net energy returns of renewable energy appear to be unfounded.

Comparative study of high-performance mesophilic and thermophilic anaerobic membrane bioreactors in the co-digestion of sewage sludge and food waste: Methanogenic performance and energy recovery potential

To support smart cities in terms of waste management and bioenergy recovery, the co-digestion of sewage sludge (SeS) and food waste (FW) was conducted by the anaerobic membrane bioreactor (AnMBR) under mesophilic and thermophilic conditions in this study. The biogas production rate of the thermophilic AnMBR (ThAnMBR) at the SeS to FW ratio of 0:100, 75:25, 50:50 and 100:0 was 2.84 ± 0.21, 2.51 ± 0.26, 1.54 ± 0.26 and 1.31 ± 0.08 L-biogas/L/d, inconspicuous compared with that of the mesophilic AnMBR (MeAnMBR) at 3.00 ± 0.25, 2.46 ± 0.30, 1.63 ± 0.23 and 1.30 ± 0.17 L-biogas/L/d, respectively. The higher hydrolysis ratio and the poorer rejection efficiencies of the membrane under thermophilic conditions, resulting that the permeate COD, carbohydrate and protein of the ThAnMBR was higher than that of the MeAnMBR. The lost COD that might be converted into biogas was discharged with the permeate in the ThAnMBR, which was partly responsible for the inconspicuous methanogenic performance. Furthermore, the results of energy recovery potential assessment showed that the energy return on investment (EROI) of the MeAnMBR was 4.54, 3.81, 2.69 and 2.22 at the four SeS ratios, which was higher than that of the ThAnMBR at 3.29, 2.97, 2.02 and 1.80, respectively, indicating the advantage of the MeAnMBR over the ThAnMBR in energy recovery potential. The outcomes of this study will help to choose a more favorable temperature to co-digest SeS and FW to support the construction of smart cities.

Evaluation of Life Cycle Assessment of Jatropha Biodiesel Processed by Esterification of Thai Domestic Rare Earth Oxide Catalysts

The Thai domestic rare earth oxides, including cerium, lanthanum, and neodymium oxides, with the effects of calcination temperatures (500–1000 °C), were utilized as catalysts for twelve Jatropha biodiesel alternatives via an esterification reaction. This study applied life cycle assessment (LCA) methodology from well-to-wheel analysis to assess energy efficiency and the global warming impact with and without land use change. The results of the life cycle analysis showed that the Jatropha biodiesel alternatives using the La2O3 catalyst in all conditions (0.89–1.06) were found to be potential fuel substitutes for conventional diesel (0.86) in terms of net energy ratios; however, the results showed that they generated a higher global warming impact. Considering the improvement process of Jatropha biodiesel in the utilization of waste heat recovery, the Jatropha biodiesel reduced the impacts of the net energy ratios and the global warming impact by 22–24% and 34–36%, respectively. The alternative Jatropha biodiesel using the La2O3 catalyst with a calcination temperature of 600 °C was shown to be the most environmentally friendly of all the studied fuels; relatively, it had the highest energy ratios of 1.06–1.37 (with and without waste heat recovery) and the lowest total global warming impact of 47.9–70.7 kg CO2 equivalent (with land use change). The integration of the material and process development by domestic catalysts and the recovery of waste heat would improve the sustainability choices of biofuel production from renewable resources for transportation fuels in Thailand.

Trade-offs between higher productivity and lower environmental impacts for biodiversity-friendly and conventional cattle-oriented systems

CONTEXTBiodiversity loss caused by livestock production is a key environmental issue. Biodiversity-friendly livestock systems aim to favour biodiversity mainly for its own sake. Environmental impacts of biodiversity-friendly livestock systems have not been studied, nor have trade-offs between higher productivity and lower environmental impacts of these systems. OBJECTIVEThis study aimed to (i) assess the productivity and environmental impacts of a sample of cattle-oriented production systems representing a wide range of external inputs, productivity and consideration of biodiversity; (ii) identify trade-offs among the objectives of lower input use, higher productivity, lower environmental impacts and higher energy return on investment (EROI); (iii) relate the systems' production strategies to the trade-offs identified and (iv) identify perspectives for biodiversity-friendly livestock systems. METHODSThis study assessed the productivity and environmental impacts of a sample of seven cattle-oriented production systems: an agricultural rewilding system (biodiversity-friendly, in England), three suckler beef systems (two of them considered biodiversity-friendly, in France) and three dairy systems (one biodiversity-friendly and one conventional, in France). Life cycle assessment (LCA) was applied to assess six environmental impacts (i.e. terrestrial acidification, freshwater eutrophication, marine eutrophication, land occupation, and in particular, climate change and energy demand) and was combined with calculation of EROI. RESULTS AND CONCLUSIONSPer hectare of land occupied to produce livestock and their feed, production of human-edible animal protein and environmental impacts of these systems increased as energy demand (i.e. input use) increased. Per hectare, human-edible animal protein production, energy demand and climate change impact (considering carbon dynamics) ranged from 5 kg, 90 MJ and −5.5 t CO2-eq., respectively, for the agricultural rewilding system to 239 kg, 20,496 MJ and 8.3 t CO2-eq., respectively, for the conventional French dairy farm. Patterns of trade-offs varied among the production strategies of the farms. The four biodiversity-friendly farms in the sample had low productivity but also low environmental impacts per ha, especially for climate change and energy demand, due to being extensive systems with relatively high self-sufficiency. Biodiversity-friendly farms also had higher EROI than other farms that produced the same products. Using LCA to assess biodiversity-friendly systems, in particular agricultural rewilding, challenges its ability to consider natural baseline emissions and non-provisioning ecosystem services. SIGNIFICANCEThese results emphasise the need to consider the multiple functions of these systems and their overall environmental performances and sustainability. Current economic and social trends may provide opportunities for biodiversity-friendly livestock systems as a possible future for livestock systems.

Developing a framework to evaluate the life cycle energy and greenhouse gas emissions of space heating systems using zeolite 13× as an adsorbent material

The wide use of fossil-based space heating systems results in significant greenhouse gas (GHG) emissions. Using solar energy for space heating can help reduce GHG emissions. However, solar energy generation is intermittent and the energy needs to be stored for continuous supply. The zeolite 13× adsorbent heat storage system for space heating is a promising alternative. There is very limited research on the life cycle GHG footprint of this type of adsorbent storage system. In this study, we developed a framework that integrates engineering design with life cycle assessment to evaluate the energy and emission performances of a zeolite 13×-based heating system charged by a solar air collector. A simulation model was developed for this adsorbent storage system. The life cycle GHG emissions of the residential heating system are estimated to be 0.1160 kg CO2 eq per kWh of the heat delivered over a 20-year lifetime. The operational phase contributes 74 % of the overall emissions because of the energy required by the humidifiers. The material production stage accounts for 25 %, mainly attributed to the upstream emissions in the manufacturing of photovoltaic thermal (PVT) air solar systems. The net energy ratio (NER), which is the ratio of energy output to fossil energy input, is 2.9. The continuous days without sunlight, the adsorbent vessel length-to-diameter ratio (L/D), and the pellet diameter of the zeolite 13× storage appear to be the parameters most sensitive to both emissions and NER. The uncertainty analysis shows emissions and NERs of the space heating system in the range of 97.2–152.3 g CO2 eq/kWh and 2.4–3.0, respectively. Compared with other alternative heating systems in the market, the adsorbent system has a much better GHG performance. The research highlights the importance of selecting a suitable space heating system given the high influence of operational energy on the life cycle emissions and the range of electricity generation emissions in different provinces.

Environmental footprint evaluation of Jatropha biodiesel production and utilization in Ethiopia: a comprehensive well-to-wheel life cycle analysis

In Ethiopia, a Life Cycle Analysis of Jatropha-based biodiesel was conducted using the Greenhouse Gases, Regulated Emissions, and Energy Use in Transportation model to assess energy consumption, efficiency, and greenhouse gas (GHG) emissions in the well-to-tank (WTT) and well-to-wheel stages. The inventory analysis involved field surveys and scenarios to evaluate energy savings, emission reductions, and air pollutants in biodiesel-diesel blends. In the WTT analysis, the energy consumption for producing 1 MJ of Jatropha-based biodiesel was found to be 0.43 MJ under rain-fed and 0.68 MJ under irrigated conditions. The net energy value was positive, and the net energy ratio was higher compared to that in other countries. The results show that GHG emissions at 19.8 g CO2 eq/MJ during the WTT stage can reduce environmental impacts by up to 45–87% depending on the type of irrigation used. When examining the global warming potential, it was found that the cultivation of Jatropha accounted for the highest share of GHG at 57.58%, followed by the biodiesel production process at 23.88%. On the other hand, vehicles employing B20 blend could replace 14.78% of fossil energy use and reduce 13.95% of GHG emissions per km, compared to pure diesel vehicle.

310 Evaluation of Orally Administered Megasphaera Elsdenii in Preconditioned Calves Abruptly Transitioned from a Receiving Diet with 4% Dietary Starch to a Growing Diet with 37% Dietary Starch

Abstract The objective of this study was to evaluate the effects of orally administered Megasphaera elsdenii NCIMB 41125 (ME) in preconditioned calves abruptly transitioned from a receiving diet with 4% dietary starch [dry matter (DM) basis] to a growing diet with 37% dietary starch (DM basis). Preconditioned steers [n = 192; initial shrunk body weight (SBW) = 309 kg ± 20.6 kg] were assigned to microbial supplement treatment in a randomized complete block design. Treatments were CON: no ME; and LP: orally administered 20 mL of microbial supplement (2 × 1010 colony forming units ME/mL) immediately before diet change. Steers were abruptly changed from a receiving diet based upon soybean hulls and wheatlage with 4% dietary starch (DM basis) to a growing diet based upon high-moisture ear corn, dry-rolled corn, and wheatlage with 37% dietary starch (DM basis). Diets were switched on an equal DM basis to achieve abrupt change and steers were fed treatment diet for 49 d until study completion. Prior to study initiation, steers (n = 72; n = 3/pen) were fitted with wireless rumination tags to track daily activity and rumination time. Growth performance data and efficiency of dietary net energy utilization were analyzed with pen as the experimental unit, fixed effect of treatment, and random effect of block (location in the feedlot). Activity and rumination data were analyzed in a repeated measures analysis of covariance with individual animal as experimental unit, fixed effects of treatment, week, and their interaction, block (location in feedlot) as a random effect, and baseline activity and rumination as a covariate in the model. If no interaction was observed, main effect means of treatment and week were evaluated independently. For all statistical analysis, P ≤ 0.05 was declared significant and P ≤ 0.10 was declared a tendency. No difference (P ≥ 0.20) was observed between treatments for final SBW, average daily gain, dry matter intake, feed efficiency, calculated net energy (NE) for maintenance and gain or observed-to-expected ratio of NE for maintenance and gain. Additionally, no treatment × day differences (P ≥ 0.27) were observed for activity or rumination measures. Treatment effects (P &amp;lt; 0.01) were observed for both activity and rumination where LP steers had a 2% increase and 2% decrease in minutes per day active and ruminating respectively. Additionally, a positive linear effect (P &amp;lt; 0.01) of week was observed for minutes ruminating and quadratic effects (P &amp;lt; 0.01) of week were observed for minutes active and ruminating. Oral administration of ME had no effects on growth performance or efficiency of dietary net energy utilization in steers transitioned from a receiving diet containing 4% starch (DM basis) to a growing diet containing 37% starch (DM basis).

A high-resolution energy use efficiency assessment of China’s staple food crop production and associated improvement potential

Improving production efficiency of existing agricultural systems is key to promoting sustainable agricultural production. Energy use efficiency in crop production is a key and widely applied index used to measure agricultural production efficiency. Understanding the current status of energy use efficiency in crop production at high spatial resolutions is requisite for developing energy-saving and efficient crop production optimization strategies. This study provides a first attempt at systematically evaluating the county-level energy use efficiency status of China’s three staple food crops (i.e., wheat, maize, and rice) and their associated improvement potential based on the Energy Return on Investment (EROI) method. Results show that average EROI values of wheat, maize, and rice production (i.e., 0.94, 1.1, and 1.3, respectively) substantiate low energy use efficiency under a high improvement potential. Moreover, the energy use efficiency of staple food crop production exhibits considerable spatial heterogeneity. The top 25% counties with the highest EROI values are mainly concentrated in wheat-producing areas of the North China Plain, maize-producing areas of northeastern China and Inner Mongolia, and rice-producing areas of the central Yangtze River region. Crop yields and agricultural machinery inputs are the main EROI driving factors. Furthermore, scenario analysis shows that regional EROI gaps in wheat, maize, and rice production could be narrowed by increasing yields and improving agricultural machinery operation efficiency. Overall, this study provides an improved understanding of the current energy use efficiency status of staple food crop production in China. Recommended solutions are also proposed to improve the EROI of staple food crops. This provides scientific support in formulating regional optimal management strategies for crop production and guidance for farmers to conduct more efficient production practices. Additionally, our framework can also be adopted and built upon in regions throughout the world that experience similar low energy use efficiency conditions in agricultural production.

Hydrothermal but Not Mechanical Pretreatment of Wastewater Algae Enhanced Anaerobic Digestion Energy Balance due to Improved Biomass Disintegration and Methane Production Kinetics

This study used pilot-scale high-rate algae ponds to assess algal–bacteria biomass productivity and wastewater nutrient removal as well as the impact of mechanical and hydrothermal pretreatments on biomass disintegration, methane production kinetics, and anaerobic digestion (AD) energy balance. Mechanical pretreatment had a minor effect on biomass disintegration and methane production. By contrast, hydrothermal pretreatment significantly reduced particle size and increased the solubilized organic matter content by 3.5 times. The methane yield and production rate increased by 20–55% and 20–85%, respectively, with the highest values achieved after pretreatment at 121 °C for 60 min. While the 1st-order and pseudo-1st-order reaction equation models fitted methane production from untreated biomass best (R2 &gt; 0.993), the modified Gompertz sigmoidal-type model provided a superior fit for hydrothermally pretreated algae (R2 ≥ 0.99). The AD energy balance revealed that hydrothermal pretreatment improved the total energy output by 25–40%, with the highest values for volume-specific and mass-specific total energy outputs reaching 0.23 kW per digester m3 and 2.3 MW per ton of biomass volatile solids. Additionally, net energy recovery (energy output per biomass HHV) increased from 20% for untreated algae to 32–34% for hydrothermally pretreated algae, resulting in net energy ratio and net energy efficiency of 2.14 and 68%, respectively.