Energy Return On Investment Research Articles

The Identification of Hotspots in the Bioenergy Production Chain

Increasing interest in bioenergy production in the context of the transition towards a circular economy and the promotion of renewable energy has produced demands for optimization of the value chain of energy production to improve the environmental viability of the system. Hotspot analysis based on life cycle assessment (LCA) contributes to the mitigation of environmental burdens and is a very important step towards the implementation of a bioeconomy strategy. In this study, hotspots identified using two parallel pathways: a literature review and empirical research on four different biogas plants located in Poland. LCA and energy return on investment (EROI) analysis of the whole bioenergy production chain were considered to identify unit processes or activities that are highly damaging to the environment. The biogas plants differ mainly in the type of raw materials used as an input and in the method of delivery. The results show that the most impactful processes are those in the delivery of biomass, especially road transport by tractor. The second contributor was crop cultivation, where fossil fuels are also used. Although the EROI analysis indicates a negligible impact of transport on the energy efficiency of bioenergy plants, the environmental burden of biomass transportation should be taken into consideration when planning further measures to support the development of the bioeconomy.

Sustainability Performance through Technology Adoption: A Case Study of Land Leveling in a Paddy Field

Energy is required in all agricultural activities. Diagramming material flows needed by crop production systems supports the proper analysis of energy flows interactions within a system’s boundaries. The latter complemented with an economic analysis gives a clear view of how beneficial a new practice within a crop cycle is—in this case, the variable slope (VS) land leveling (LL) operation. VS is a global navigation satellite system (GNSS, with real time kinematics—RTK—accuracy) LL technique used to create a smooth continuous surface with a constant slope, by cutting and filling topsoil layers only in those points presenting “anomalies” of micro-relief which make the movement of water difficult. This operation is important for paddy production since: (i) it enables to crop during dry seasons by harnessing the water of rivers and wells, and (ii) improves the production during rainy seasons, by allowing the farmer to manage the drainage timely and homogeneously. The present study aims to analyze, from the energy perspective, the effects of the VS leveling implementation in a paddy field (located in the Costa Rican Pacific), throughout input (labor, gas oil, etc.) and output (yield and price) data of five consecutive years (2011–2015). A material flow diagram was created representing two scenarios: before and after leveling the land. The materials were converted into energy (MJ ha−1) data, used for the estimation of EROI (energy return on investment), EP (energy productivity) and EB (energy balance) indices, while looking for a clearer understanding of the LL impact on the use of energy within the agroecosystem. Moreover, in order to complement the energy perspective, an economic point of view was considered as well through a profitability analysis where the total gain obtained over the years with LL was compared with that obtained without LL. Results showed that the increase in energy consumed by incorporating VS leveling is compensated by the gradual increase of energy embodied in yield, increasing energy balance (EB) from 26,192 MJ ha−1 up to 91,166 MJ ha−1. Similarly, EROI and EP were duplicated with LL. Economic total gain after incorporating the VS increased from less than 500 USD ha−1 up to 1800 USD ha−1 in the third year after leveling. Yield is more affected under adverse weather conditions with irregular water supply, either limited or excessive; and effects are less pronounced when the yield limiting factor is associated with biotic stress unrelated to irrigation and drainage facts. An environmental positive impact should also be noted, since VS allowed the production benefits of having highly-efficient irrigation and drainage systems, while avoiding major damage to topsoil layers.

Energy payback time analysis and return on investment of off-grid photovoltaic systems in rural areas of Tanzania

Owing to a vast land area, abundant solar radiation, and overseas support, the use of photovoltaics (PV) as a source of electricity is rapidly spreading in Sub-Saharan Africa. To understand the actual application situations, two cases of PV electricity generation systems in the rural areas of Tanzania were investigated via life cycle assessment. The energy payback time (EPBT) calculated from the utilisation of the PV systems, taking into consideration the inventory data of the International Energy Agency, revealed an unsatisfactory performance. Specifically, the EPBTs based on actual power generation at the sites greatly exceeded the expected value-based solar radiation calculations. At one site, the EPBT even exceeded the lifespan of the PV panel, indicating that energy recovery was impossible. With respect to the energy return on investment (EROI), it was evident that the income generated from the investments was insufficient to cover current operational costs, suggesting negative returns on investment. Conversely, diesel power generation appeared to be more suitable in these areas owing to the low and discontinuous demand for power. Furthermore, the operation of a more efficient PV system would require improved maintenance and management, as well as an increase in the demand for electricity.

Practical Applications of Net Energy Analysis of Upstream Oil and Gas Processes

Abstract Net energy analysis (NEA) has traditionally been utilized by nonindustry actors, such as academics, economists, and regulators. It has not been widely accepted as a beneficial method within the oil and gas industry with regard to oil extraction systems. This research describes several NEA metrics, such at the energy return on energy investment (EROI), and the energy intensity ratio (EIR), and suggests several practical benefits to oil and gas owner/operators of applying them. The benefits are primarily realized by integrating NEA into economic analysis at the field level, facility level, and well level. The high level impact of energy on both capital and operational (OPEX and CAPEX) expenditures is explored. The case is made that NEA can be used to illuminate the drivers behind energy intensive oil and gas extraction processes, and thus can be used to reveal important economic risks and opportunities.

Torrefaction of fruit peel waste to produce environmentally friendly biofuel

This study torrefied Ananas comosus peel (ACp) and Annona squamosa peel (ASp) samples at different temperatures (210–300 °C) for different durations (30 and 60 min) to produce biochar as a renewable energy source. Analysis results indicated that the torrefaction temperature, not the reaction duration, had a dominant influence on the characteristics of the produced biochar. The ACp biochar had a maximum higher heating value (HHV) of 27.7 MJ/kg and maximum energy density of 1.58, which were higher than those of the ASp biochar. As the torrefaction temperature and time increased, the fixed carbon and ash contents and the fuel ratio (FR) increased gradually for both types of biochar, but the volatile matter content and energy return on investment (EROI) decreased. The hydrogen/carbon and oxygen/carbon atomic ratios of both types of biochar are comparable to those reported for lignite. Thermogravimetric and derivative thermogravimetric analyses confirmed that the thermal stability of both types of fruit waste increased considerably with the torrefaction temperature. Furthermore, the ACp biochar had a maximum EROI of 22.9 and FR of 0.36. When 10%–20% biochar was cofired with 80%–90% bituminous coal in a power plant, the FR (1.80–1.84 and 1.60–1.67)—representing combustion efficiency—approximated that of bituminous coal (1.5–2.5), but greenhouse gas (GHG) emissions decreased significantly (83.7%–94.3%). Taken together, the cofiring of ACp biochar or Asp with coal is potentially viable and economically beneficial for increasing the HHV, energy density, fixed carbon content, FR, and EROI of these materials while reducing GHG emissions, rendering these materials suitable for partially replacing bituminous coal in power plants.

An Assessment of Civil Nuclear ‘Enabling’ and ‘Amelioration’ Factors for EROI Analysis

Nuclear fission is a primary energy source that may be important to future efforts to reduce greenhouse gas emissions. The energy return on investment (EROI) of any energy source is important because aggregate global EROI must be maintained at a minimum level to support complex global systems. Previous studies considering nuclear EROI have emphasised energy investments linked to ‘enabling’ factors (upstream activities that enable the operation of nuclear technology such as fuel enrichment), have attracted controversy, and challenges also persist regarding system boundary definition. This study advocates that improved consideration of ‘amelioration’ factors (downstream activities that remediate nuclear externalities such as decommissioning), is an important task for calculating a realistic nuclear EROI. Components of the ‘nuclear system’ were analysed and energy investment for five representative ‘amelioration’ factors calculated. These ‘first approximation’ calculations made numerous assumptions, exclusions, and simplifications, but accounted for a greater level of detail than had previously been attempted. The amelioration energy costs were found to be approximately 1.5–2 orders of magnitude lower than representative ‘enabling’ costs. Future refinement of the ‘amelioration’ factors may indicate that they are of greater significance, and may also have characteristics making them systemically significant, notably in terms of timing in relation to future global EROI declines.

Modelling of a Brazilian ethanol plant: impact of the bagasse use and the ethanol dehydration on energy efficiency and sustainability

Ethanol has a large share in Brazilian primary energy consumption and plays a significant role in the mitigation of the emissions from combustion engines, as national regulations advance towards increasing anhydrous ethanol content in gasoline or by the direct use of hydrated ethanol as fuel. A simulation of a sugarcane ethanol plant with a regular yield of 85.3 L of ethanol per ton of cane was carried out. The investigated process starts from the cultivation of sugarcane to the production of hydrated and/or anhydrous ethanol. The study considered that bagasse can be either burnt for cogeneration or used as feedstock for the enzymatic hydrolysis system. Additionally, alternative energy sources (such as natural gas (NG) burnt in a boiler or electricity from the Brazilian National Interconnected System (NIS)) are considered in order to cover the domestic demand in cases where biomass lacked for energy purposes. Net energy ratio (NER), fossil energy ratio (FER) and total CO2 emission were modelled through central composite designs to assess scenarios in which the fraction of bagasse sent to hydrolysis (x1) and hydrated ethanol sent to dehydration (x2) both varied between 0 and 100%. The application of statistical tools (ANOVA, Student’s t test and R2) showed that x1 caused significant variations on the investigated parameters, while x2 proportioned mild effects. NER varied in the range 0.795–0.984, with an optimal value being found at (x1, x2) equal to (81.82, 0) and (36.67, 0) when the system is coupled to NIS and a NG boiler, respectively. FER was verified as high as 11.910 with energy from NIS to produce hydrated ethanol with maximal cogeneration from the bagasse. It diminished to 3, when around 40% of bagasse is sent to enzymatic hydrolysis instead for the cogeneration system and NG complements the domestic demand.

Declines in EROI of Main Fuels and the Implications on Developing LNG as a Marine Fuel

This article proposes an analytical model for a conversion from Heavy Fuel Oil (HFO) to Liquide Natural Gas(LNG) dual-fuel engine in a fleet with three sizes of vessels in order to investigate the impact of the volatility of oil prices, and a declining Energy Return on Investment (EROI) on opting LNG as a reliable marine fuel. This study also attempts to echo the importance of looking through a new window to the process of energy opting in the maritime industries to comply with International Maritime Organization (IMO) regulations. With giving this awareness to the maritime society the new investment can be directed to resources that effectively keep the maritime economy growing and can also help build a sustainable future. In order to find the best answer, we need to seek alternative solutions that will sustain shipping’s competitive edge. In the first phase, the impact of a declining EROI gas is investigated. Then, in the second phase, to be able to find an optimal area to run the vessels, we apply the Computerized Engine Application System (CEAS) in order to predict the engine performance of different container vessels and outlined fuel consumption in various market and technical situations. Since the process found is a non-linear system, this paper attempts to investigate the ongoing trend of the EROI of LNG in applying a Net Present Value (NPV) as a simulation method in order to observe the system to which technical variables or legal frameworks is more sensitive. In the following order, we first characterise the uncertainty faced by policy-makers and complexity dynamics implications for investment decision-makers and technology adoption. The practical relevance here of the proposed applied methodology is subsequently discussed in reference to four scenarios relating to the above areas and introduces the most beneficial area between different vital variables and constraints. It is applicable for the management of cascading uncertainties and the cross-sectoral impact by introducing the most beneficial area between various vital variables and constraints; including LNG prices, Capital Expenditure (Capex), Operating Expenditure(Opex) and time of enforcement.

Exploration of the environmental implications of ageing conventional oil reserves with relational analysis

A novel method based on relational analysis is presented for assessing the performance of conventional oil exploitation and its environmental implications, with a focus on the energy-water nexus. It considers the energy system as a metabolic network and integrates various factors relevant for technical, economic and environmental processes, thus avoiding some of the simplifications inherent in conventional approaches to the assessment of primary resource quality, such as economic cost-benefit analysis (CBA) and the energy return on investment (EROI). Relational analysis distinguishes between functional (notional) and structural (tangible) elements in the metabolic network, which allows a simultaneous characterization and geo-localization of the exploitation process across different scales and dimensions of analysis. Key aspects of the approach are illustrated with data from the Ecuadorian oil sector spanning the period 1972–2018. It is shown that by establishing a relation among the characteristics of the exploited oil fields (oil typology, age of field) and those of the exploitation process (requirement of energy carriers, labor, freshwater and power capacity and generation of greenhouse gases and oil-produced water), changes in the performance and environmental implications of the oil extraction system can be characterized at different points in space and time.

Novel Solar Parabolic Trough Collector cum Reactor for the Production of Biodiesel from Waste Cooking Oil using Calcium Oxide catalyst derived from seashells waste

Waste cooking oil was converted to biodiesel using a parabolic trough collector using solar radiations as a heating source and a parabolic trough collector as an intensifier. Calcium oxide (CaO) derived from seashells was used as a catalyst in order to boost the rate of the reaction. Temperatures of almost 95 °C were reached using this collector although the temperature was limited to below 78.4 °C in order to prevent the vaporization of ethanol. The influence of different parameters on the reaction was analyzed. The maximum yield was found to be 95.84%, obtained under conditions of 180 LPH reactant flow rate, 300 rpm stirring speed, 60 minutes reaction time, 9:1 ethanol to oil ratio and 90 cm catalyst bed height. The composition and properties of the biodiesel were found to be in accordance with literature and ASTM and BIS norms. The energy efficiency of the process was analyzed by net energy ratio (NER). The net energy efficiency index (NEEI) was obtained from the ratio of NER of the solar method to the conventional method. NEEI of the process was found to be 4.16, thereby making the process a highly promising method of biodiesel production.

Dual production of bioenergy in heterotrophic cultures of cyanobacteria: Process performance, carbon balance, biofuel quality and sustainability metrics

This research evaluated the dual production of bioenergy in heterotrophic cultures of cyanobacteria. Process performance parameters, carbon balance, single-cell oil production, biofuel quality, volatile organic compounds (VOCs) generation, and sustainability metrics and impact indicators were assessed. The results showed biomass productivity of 1.03 kg/m³/d. Biomass (63.9%) and VOCs (8.56%) were the main products formed from the conversion of the substrate in the bioreactor. For single-cell-oil production, it is possible to obtain 0.18 kg/m³/d of lipid with this bioprocess. It was determined the fatty acid profile and the quality of biodiesel properties, meeting the requirements established by national and international standards. Besides, the 22 volatile compounds identified presented the energy potential of 122,205.00 kJ/kg and a power generation rate of 10,580.5 kg/m3/d. From an environmental point of view, the net energy ratio was 0.13, while the eight mid-points impact categories resulted in an ecotoxicity potential of 430.86 CTUe, energy resources of 230.04 MJ, global warming of 171.05 kg CO2 eq, photochemical oxidation of 1.33 kg O3 eq, water footprint of 1.08 m³, acidification of 0.44 kg SO2 eq, eutrophication of 0.13 kg N eq, and ozone depletion of kg 1.83 × 10−5 CFC-11 eq, per functional unit of 1 m³ of the bioreactor, operating for 5 days. Finally, the proposed process can be considered as a promising strategy for renewable energy production from microalgae.

Is aquatic bioenergy with carbon capture and storage a sustainable negative emission technology? Insights from a spatially explicit environmental life-cycle assessment

It is anticipated that achievement of the Paris Climate Agreement goals will require widespread deployment of negative emission technologies (NETs). The most prominent NET is bioenergy with carbon capture and storage (BECCS), which is typically envisioned to use terrestrial crops as feedstock. Several recent studies have focused on aquatic BECCS (A-BECCS), making use of microalgae or macroalgae as feedstock, as possible means of reducing water and land use. However, the high logistical complexity of the A-BECCS supply chain makes it likely that regional biophysical and socio-technical factors will strongly influence its overall favorability. Therefore, this study applies life-cycle assessment (LCA) incorporating a geographic information system (GIS) framework to estimate the environmental impacts of A-BECCS over all stages of its life-cycle. Three candidate locations in the USA are evaluated based on seemingly good proximity to coastal regions and CO2 storage; namely, East Coast, West Coast, and the Gulf of Mexico. Monte Carlo simulation is used to characterize distributions of model outputs, including energy return on investment (EROI) and net global warming potential (GWP). Results reveal that only the Gulf of Mexico configuration has any likelihood of achieving both net energy production (probability of EROI > 1 = 29%) and net CO2 sequestration (probability of GWP < 0 = 6%), but the probability of achieving both together is very low (5%). The other two locations exhibit net positive energy production (EROI > 1), but not net negative carbon sequestration. These results call into question the feasibility of the modeled A-BECCS system as an energy-producing NET and offer insights into possible system reconfiguration. For example, anaerobic digestion offers very low EROI and creates multiple carbon-bearing waste streams, which strongly undercuts overall net CO2 sequestration. Finally, it is observed that enhanced oil recovery (EOR) strongly contributes to net-energy production (EROI > 1) in the modeled A-BECCS system, but also strongly undercuts net CO2 sequestration, which is arguably the main goal of any NET. This analysis showcases how geographically-explicit analysis can advance our understanding of biomass-based NETs.

The influence of the investment factor on the transformation of the global energy market

The object of the study is the transformation of the world energy market under the influence of investment. The study of the impact of investments on the transformation of the world energy market was carried out in terms of market, structural, and organizational parameters in the following areas:– the growing role of renewable sources in the world energy balance;– liberalization of sectoral energy markets;– wide application of information technologies, including the introduction of Smart Grid at various levels.The main disadvantages are the inability to analyze the transformation processes in all sectors of energy at the global level.Such general scientific and special methods as methods of analysis and synthesis, method of comparative analysis, graphic and statistical methods were used in the research.The paper shows that at the present stage the main prerequisite for investment has been the COVD-19 pandemic and pre-crisis expectations. This has led to a sharp decline in global investment in all energy sectors (both in aggregate energy supply and in end-use) and in research and development. In terms of industry, investments in oil and oil products (by all organizational forms of companies) and coal decreased the most. Investment in electricity and electricity networks exceeds investment in mining and processing of fossil fuels. The main factors holding back international investment in renewable energy are:– relatively lower economic and energy return on investment (EROI);– the high cost of connection to power systems;– local component requirements and other protectionist requirements;– discrediting by global oil and gas corporations about the danger of economic downturn and job cuts, etc.In the regional structure, the largest volumes of global investment are in the Asia-Pacific region, North America, and Europe.Insufficient investment in the accelerated transformation of the world energy market on the basis of sustainable development has been stated in all areas. The targeted efforts of both national governments and the international community are needed to ensure the desired transformation of the global energy market.

Rice-pasture agroecosystem intensification affects energy use efficiency

Sustainable rice production systems are key to food security. Diversified farming systems are essential for ecological intensification and environmental enhancement. Energy use efficiency is one of the main sustainability indicators in agroecosystems. Thus, an assessment of consumption and efficiency of energy in contrasting cropping systems can discriminate their management practices and components sustainability. The goal of this study was to evaluate the energy performance through energy return on investment (EROI) in four rice-based rotation systems that belong to a long-term experiment located in the Temperate Grassland Terrestrial Ecoregion, at the Atlantic side of South America. Rotations analyzed consisted in: a) continuous rice (Rc); b) rice-soybean (R−S); c) rice-pasture for 1.5 years (R−PS); and, d) rice-pasture for 3.5 years (R−PL). The EROI estimations considered all the inputs and outputs of energy from cradle to farm gate. The greatest EROI was observed in R–S (7.2 MJMJ−1) and the lowest energy consumption in R−PL (10,607 MJ(hayr)−1). The R−PL’s EROI (6.7 MJMJ−1) was 6.5% and 8% higher than Rc and R−PS EROI, respectively. Rotations without pastures produced 79% more energy compared with rotations including pastures. However, energy inputs of rice-pasture rotations were 40% lower than either R−S or Rc. The EROI (without animal production) of R−PS, R–S and Rc was 25%, 28% and 43% lower than the EROI of R−PL (10 MJMJ−1), respectively. For the analyzed South American ecoregion, EROI assessments of four business as usual rice production systems allowed to discriminate and hierarchize their sustainability and diversity.

Potential of conservation agriculture modules for energy conservation and sustainability of rice-based production systems of Indo-Gangetic Plain region

Rice-based cropping systems are the most energy-intensive production systems in South Asia. Sustainability of the rice-based cropping systems is nowadays questioned with declining natural resource base, soil degradation, environmental pollution, and declining factor productivity. As a consequence, the search for energy and resource conservation agro-techniques is increasing for sustainable and cleaner production. Conservation agriculture (CA) practices have been recommended for resource conservation, soil health restoration and sustaining crop productivity. The present study aimed to assess the different CA modules in rice-based cropping systems for energy conservation, energy productivity, and to define energy-economic relations. A field experiment consisted of four different tillage-based crop establishment practices (puddled-transplanted rice followed by (fb) conventional-till maize/wheat (CTTPR-CT), non-puddled transplanted rice fb zero-till maize/wheat (NPTPR-ZT), zero-till transplanted rice fb zero-till maize/wheat (ZTTPR-ZT), zero-till direct-seeded rice fb zero-till maize/wheat (ZTDSR-ZT)), with two residue management treatments (residue removal, residue retention) in rice–wheat and rice–maize rotations were evaluated for energy budgeting and energy-economic relations. Conservation-tillage treatments (NPTPR-ZT, ZTTPR-ZT, and ZTDSR-ZT) reduced the energy requirements over conventional tillage treatments, with the greater reduction in ZTTPR-ZT and ZTDSR-ZT treatments. Savings of energy in conservation-tillage treatments were attributed to reduced energy use in land preparation (69–100%) and irrigation (23–27%), which consumed a large amount of fuel energy. Conservation-tillage treatments increased grain and straw/stover yields of crops, eventually increased the output energy (6–16%), net energy (14–26%), energy ratio (25–33%), and energy productivity (23–34%) as compared with CTTPR-CT. For these energy parameters, the treatment order was ZTDSR-ZT ≥ ZTTPR-ZT > NPTPR-ZT > CTTPR-CT (p < 0.05). Crop residue retention reduced net energy, energy ratio, and energy productivity when compared with residue removal. Our results of energy-economic relations favored the “conservative hypothesis,” which envisages that energy and monetary investments are not essentially the determinants of crop productivity. Thus, zero tillage-based crop establishments (ZTTPR-ZT, ZTDSR-ZT) in rice-based production systems could be the sustainable alternative to conventional tillage-based agriculture (CTTPR-CT) as they conserved non-renewable energy sources, reduced water requirement, and increased crop productivity.

Willow Biomass Crops Are a Carbon Negative or Low-Carbon Feedstock Depending on Prior Land Use and Transportation Distances to End Users

Few life cycle assessments (LCAs) on willow biomass production have investigated the effects of key geographically specific parameters. This study uses a spatial LCA model for willow biomass production to determine spatially explicit greenhouse gas (GHG) emissions and energy return on investment (EROI), including land use conversion from pasture and cropland or grassland. There were negative GHG emissions on 92% of the land identified as suitable for willow biomass production, indicating this system’s potential for climate change mitigation. For willow planted on cropland or pasture, life cycle GHG emissions ranged from −53.2 to −176.9 kg CO2eq Mg-1. When willow was grown on grassland the projected decrease in soil organic carbon resulted in a slightly positive GHG balance. Changes in soil organic carbon (SOC) associated with land use change, transportation distance, and willow yield had the greatest impacts on GHG emissions. Results from the uncertainty analysis exhibited large variations in GHG emissions between counties arising from differences in these parameters. The average EROI across the entire region was 19.2. Willow biomass can be a carbon negative or low-carbon energy source with a high EROI in regions with similar infrastructure, transportation distances, and growing conditions such as soil characteristics, land cover types, and climate.

Slow pyrolysis as a platform for negative emissions technology: An integration of machine learning models, life cycle assessment, and economic analysis

Biochar sequestration has gained increasing attention as a negative emissions technology to mitigate climate change. Although pyrolysis is a commercial technology, comprehensive environmental and economic assessments have been difficult to perform since biochar can be produced from a wide range of feedstocks and pyrolysis conditions. Many researchers have evaluated the environmental and economic impacts of biochar-based CO2 sequestration systems. However, most studies either worked on a single type of biomass under varying pyrolysis conditions or multiple feedstocks under the same pyrolysis conditions. To address this knowledge gap, we evaluated the energy, climate change, and economic performance of slow pyrolysis of multiple feedstocks under various processing conditions via the integration of machine learning approaches, life cycle assessment (LCA), and economic analysis. Machine learning models (i.e., random forest) were developed by fitting existing laboratory data. The models were then used to predict the yields and characteristics of biochar produced from slow pyrolysis of different feedstocks under designed processing conditions. The results were further integrated with LCA and economic analysis to compute three important metrics: energy return on investment (EROI), net global warming potential (GWP), and minimum product selling price (MPSP). The results indicate that random forest models offer good prediction accuracy for laboratory-scale (R2 = 0.78–0.87) and pilot-scale pyrolysis data (R2 = 0.45–0.65). LCA and economic analyses reveal that feedstock characteristics and pyrolysis temperature affect energy, climate change, and financial performance. Our results demonstrate slow pyrolysis of crop residues and woody wastes holds promise as an energy-producing negative emissions technology, with EROI values from 1.9 to 3.6 (without substitution) and 2.4 to 4.3 (with substitution), and GWP values from −470 kg CO2 eq/t to −200 kg CO2 eq/t (without substitution) and −1050 kg CO2 eq/t to −770 kg CO2 eq/t (with substitution). The MSPS values evaluated in this study range from $774–1256/t, depending on temperature and feedstocks. A tradeoff between environmental and economic performance is observed. The best overall energy and climate change performances are achieved via pyrolysis of lignocellulosic biomass at high temperature, while the best MPSP is achieved with the pyrolysis of sludge at low temperature.

Improving the economic feasibility of biodiesel production from microalgal biomass via high‐value products coproduction

Microalgal biodiesel has emerged as a promising fuel source, but has still not been adopted commercially. One of the several inherent challenges is its high production cost, which mandates the need to develop an integrated process to produce other valuable coproducts economically. This article combines life cycle assessment and preliminary life cycle cost assessment of a proposed biorefinery, in which a high value product, β-carotene, is coproduced from microalgae with biodiesel. The GaBi 6 environmental management software was employed to investigate the environmental impact associated with the production life cycle. The mass flow rates and the energy consumed in all stages of biodiesel and β-carotene coproduction for the functional unit of 1 kg of biodiesel were assessed. When the coproduction of β-carotene was not taken into consideration, the total energy input for a functional unit of 1.0 kg biodiesel/m2/y and the net energy ratio, that is, energy returned on energy invested were estimated to be 128.1 GWh/y and 0.27, respectively. The life cycle cost analysis showed that although the total production cost associated with coproduction of β-carotene from Dunaliella salina was higher than that of the sole production of biodiesel, it generates a hiked revenue of up to $37 million/y. Over the system lifetime of 10 years, the sole production of biodiesel showed a loss of US$345 million per functional unit, whereas the coproduction of β-carotene achieved a net profit of US$120.7 million per functional unit. This work clearly showed that the coproduction of β-carotene with biodiesel from D. salina overcomes the cost-ineffectiveness resulting from the production of biodiesel alone.

Techno-economic evaluation of third-generation bioethanol production utilizing the macroalgae waste: A case study in Malaysia

Production of third-generation bioethanol from macroalgae cellulosic residue (MCR) has received increasing interest from researchers to utilize waste for valuable product creation effectively. In this study, a techno-economic assessment to produce anhydrous bioethanol from MCR in Malaysia had been conducted by using Aspen Plus V10 and other computer-aided softwares. Kota Kinabalu Industrial Park at Sabah was identified and selected as a proper location to produce the anhydrous bioethanol based on a framework structured by the Triple Bottom Line. The overall results from the present study showed that 15833.3 kg/h of MCR was required to produce 7626 kg/h of anhydrous bioethanol. It was also found that the energy utilization could be reduced up to 32% with net energy ratio of 0.53 after implementing the Heat Exchanges Networks Synthesis and a series of process optimization. In 20 years of plant life, the pay-back period was 8 years with an internal rate of return of 23.17%. The minimum selling price of anhydrous bioethanol was estimated to be $ 0.54/kg and able to compete with the market prices of bioethanol derived from other feedstocks.

Algae-Based Beneficial Re-use of Carbon Emissions Using a Novel Photobioreactor: a Techno-Economic and Life Cycle Analysis

Despite the many advantages of microalgae, the feasibility of large-scale cultivation requires significant amounts of carbon dioxide (CO2) to enable high growth rates. A synergistic union typically proposed for the supply of CO2 is the coupling of algal cultivation with emissions from power plants. This study investigates the sustainability of a novel microalgae platform coupled with coal-based flue gas. The proposed system consists of a novel photobioreactor (PBR) for the production of biomass followed by a two-stage dewatering process. A systems model, which quantifies the CO2 and energy consumption of the proposed system, was developed, and the minimum biomass selling price (MBSP) was determined by a techno-economic analysis (TEA). TEA results indicate that a facility with the capacity to capture 30% of the emissions from a 1-MW power plant requires a biomass production of 1280 metric ton per year, which when scaled to a nth of kind facility can produce biomass at a MBSP of $2322 per ton. The environmental impact of the proposed facility was determined by a life cycle assessment methodology, and results indicate a carbon capture potential of 1.16 × 104 metric tons of CO2 equivalent. In addition, an energy analysis indicates a desirable net energy ratio of 0.1, which is lower than conventional PBRs. Discussion focuses on the requirements to reduce biomass production cost, including research investment areas for increasing productivity while decreasing energy requirements.