Small-scale Biorefineries Research Articles

Critical analysis of the use of white-box versus black-box models for multi-objective optimisation of small-scale biorefineries

Biorefinery systems that are embedded in their local setting provide an attractive framework for the valorisation of locally available food- and other bio-waste streams. They can aid in the provision of local bio-waste processing facilities as well as the targeted revalorisation of local bio-waste feedstocks by converting them in locally desired biorefinery products. Since food- and other bio-waste feedstocks are often diffuse feedstocks, small-scale biorefineries that are tailored for their local setting are the most suitable biorefining system for their processing. Whereas small-scale biorefineries cannot rely on the economy-of-scale to be an economic sustainable endeavour, they need to be meticulously optimised according to multiple sustainability objectives. These objectives can be of economic, societal, or environmental nature. A commonly used optimisation criterion in these problems is the energy requirements of the entire biorefinery system. For many commonly used biorefinery processes mass balance models are available (which are often mechanistic models), however, energy balances are difficult to obtain. Chemical process simulators, like Aspen Plus, provide an extensive toolkit to easily model the mass- and energy balances of a multitude of chemical processes. However, especially in the context of multi-objective optimisation, the obtained white-box models are too complex to simulate the considered processes efficiently consecutively. Therefore, in this contribution, a critical analysis is presented of the use of white-box versus the black-box models in the context of the multi-objective optimisation of a small-scale biorefinery. An in-house developed biorefinery network is re-modelled in Aspen Plus and used as a digital twin for the development of a surrogate model. Eventually, the modelled biorefinery network is optimised using both models and a comprehensive evaluation is drafted.

Techno-Economic and Life Cycle Assessment of a Small-Scale Integrated Biorefinery for Butyric-Acid Production in Chile

This study evaluates the techno-economic and environmental feasibility of a small-scale biorefinery in Chile’s La Araucanía Region, which utilizes wheat straw as feedstock to produce butyric acid using Clostridium tyrobutyricum. Two scenarios were considered; the standalone wheat straw biorefinery and its integration with the anaerobic digestion of pig manure for biogas production, coupled with a cogeneration system, using the xylo-oligosaccharides and lignin obtained in the pretreatment. The simulations were carried out using Aspen Plus, while the Aspen Process Economic Analyzer was used to perform the economic evaluation. The simulation results were validated with experimental data from the literature. An economic assessment was performed considering the different processes involved. A cradle-to-gate life-cycle analysis (LCA) was also applied to evaluate the different environmental impacts. Both studied scenarios were economically feasible, with the highest butyric acid production cost being USD 2.97/kgbutyricacid; however, this value is still higher compared to corn-based biorefineries. Annexed biogas production increased the costs and was less economically attractive. Nonetheless, the integrations with biogas production had lower environmental impacts, except in the photochemical oxidant formation category, which was higher because of the combustion gases obtained by the cogeneration system. A lower carbon footprint (23.5 kg CO2-eq. per ton of wheat straw) was obtained for the scenario including biogas production.

Alternatives for the Valorization of Avocado Waste Generated in the Different Links of the Value Chain Based on a Life-Cycle Analysis Approach

This work evaluates the sustainability of small-scale biorefineries as a potential enterprise alternative to be introduced in rural areas based on experimental and simulation data. Four scenarios were evaluated: the first scenario involves the production of guacamole, the second involves the production of animal feed, and the third and fourth scenarios involve the extraction of bioactive compounds and the production of avocado oil or animal feed, respectively. In addition, all scenarios produce biogas and fertilizer. Each of the scenarios were evaluated considering the technical, economic, environmental, and social aspects. As a main result, the first scenario showed the lowest operating and investment costs, as well as the lowest economic profitability (profit margin 35%). On the other hand, the third and fourth scenarios present the highest investment and operating expenses (OpEx USD 6.2 million per year and CapEx USD 1.0 million), but their profit margins are in the 60–70% range. Furthermore, a life-cycle assessment (LCA) was carried out and allows inferring that the transformer link presents the highest environmental impact of the entire value chain and that the carbon footprint for all scenarios ranges between 1.01–2.41 kg CO2 eq per kg avocado. Similarly, the social impact methodology shows that the proposed scenarios do not present any social risk. Thus, the biorefinery for animal feed, bioactive compounds, biogas, and fertilizer was selected as the best option to be implemented in Caldas.

Reducing energy poverty in small rural communities through in situ electricity generation

Energy is key in achieving sustainable societies. There have been great efforts towards improving energy access worldwide. Despite the advances in energy access, energy poverty remains a major problem in many parts of the world, particularly in rural communities. Modern energy, in particular electricity, can help rural communities develop through improving education and health. During the last two decades, there have been improvements on bioenergy technological innovations, e.g. electricity generation from bioenergy from residual biomass from several agricultural crops in biorefineries. Most research has focussed on large biorefineries, with limited research on small-scale gasifiers’ location and contribution to energy poverty. This paper is aimed at assessing technological options to generate electricity in situ from biomass to reduce energy poverty of rural communities. This is done using four analysis methods: (1) crops availability data; (2) poverty and marginalisation data; (3) electricity provision/distribution; and, (4) GIS/Geographical latitude and longitude to locate municipalities in Mexico. The results shows that the generating potential for electricity using residual biomass with gasifiers could improve the welfare of almost 10 million people communities using residual biomass from crops harvested in such communities. This research provides location solutions on the best places to locate small-scale biorefineries. The research also provides systemic analysis to reduce energy poverty through in situ electricity generation using cheap accessible small plant technologies and biomass as raw material, as well as their location. Generating electricity in a decentralised way through agricultural residual biomass can help lift rural communities from poverty and improve their well-being, and, thus, make societies more sustainable.

Prefeasibility analysis of small-scale biorefineries: the annatto and açai case to improve the incomes of rural communities

Prefeasibility analysis of small-scale biorefineries: the annatto and açai case to improve the incomes of rural communities

Environmental life cycle assessment (E-LCA) and social impact assessment (SIA) of small-scale biorefineries implemented in rural zones: the avocado (Persea Americana var. Americana) case in Colombia.

The objective of this study is to compare the environmental and social performance of two small-scale avocado biorefineries implanted in a rural zone in the North of Colombia. Two small-scale biorefineries were proposed. Small-B1 addressed to produce avocado oil and animal feed, and Small-B2 focused on the guacamole production. The environmental analysis was done by applying the life cycle assessment methodology. Then, agronomic information and process simulation were required to complete the analysis. Moreover, the water footprint of the avocado crops was estimated. Both biorefineries were compared with the direct avocados production and commercialization. The social assessment was achieved by the estimation of quantitative indicators related to wages, jobs, and working hours. The agricultural carbon and water footprints of the creole avocado crop were 0.59kg CO2-eq/kg and 2.13 m3/kg. In the same way, Small-B1 and Small-B2 obtained a carbon and water footprints of 8.99kg CO2-eq/kg and 6.63 m3/kg and 0.72kg CO2-eq/kg and 1.38 m3/kg, respectively. The hotspots of the creole avocado crop are related to the use of fertilizers and fungicides. Then, new strategies should be implemented to reduce the farmer's dependency. The social analysis exhibit a high resilience of the Small-B1 biorefinery since a salary increase to worker about 50% can be proposed. In addition, the installation of this biorefinery can create more than ten jobs. A disjunction was found between the economic, environmental, and social analyses. Thus, the need to establish a multidimensional strategy to design sustainable biorefineries is presented.

Design, Implementation and Simulation of a Small-Scale Biorefinery Model

Second-generation biomass is an underexploited resource, which can lead to valuable products in a circular economy. Available locally as food waste, gardening and pruning waste or agricultural waste, second-generation biomass can be processed into high-valued products through a flexi-feed small-scale biorefinery. The flexi-feed and the use of local biomass ensure the continuous availability of feedstock at low logistic costs. However, the viability and sustainability of the biorefinery must be ensured by the design and optimal operation. While the design depends on the available feedstock and the desired products, the optimisation requires the availability of a mathematical model of the biorefinery. This paper details the design and modelling of a small-scale biorefinery in view of its optimisation at a later stage. The proposed biorefinery comprises the following processes: steam refining, anaerobic digestion, ammonia stripping and composting. The models’ integration and the overall biorefinery operation are emphasised. The simulation results assess the potential of the real biowaste collected in a commune in Flanders (Belgium) to produce oligosaccharides, lignin, fibres, biogas, fertiliser and compost. This represents a baseline scenario, which can be subsequently employed in the evaluation of optimised solutions. The outlined approach leads to better feedstocks utilisation and product diversification, raising awareness on the impact and importance of small-scale biorefineries at a commune level.

Assessing the Local Biowaste Potential of Rural and Developed Areas Using GIS-Data and Clustering Techniques: Towards a Decision Support Tool

As the chemical and energy producing industries are steadily transitioning towards more sustainable processing practices, renewable biomass resources are becoming increasingly more valuable. Recently, following the realisation that renewable resources for the chemical and energy industry should not compete with food supplies, the use of plant-based biowaste has significantly gained in interest. Due to its inherently variable composition, diffuse distribution, and seasonality, it is of the utmost importance that (potential) biorefinery exploiters are well informed of the biowaste resources that are available in the vicinity of their (planned) biorefinery. Designing a biorefinery in such a way that it can tailor for the locally available biowaste resources, exhibits several compelling advantages. Apart from significantly reduced logistics costs, the usage of local biowaste can be a reciprocal advantage for both the involved community and the biorefinery. In this paper, a GIS-based (Geo-Information System) bio-inventory toolbox is presented. The toolbox is developed to aid the biorefinery designers and decision makers, e.g., governmental bodies, to get an adequate overview of the locally available plant-based biowaste resources and, linked to this, the expected periodical amounts, their composition, and their seasonality. The toolbox presented in this contribution is the first part of a decision support tool for the development of a locally embedded flexi-feed and small-scale biorefinery, additionally consisting out of a process modelling tool, and an optimisation tool. Both of these additional tools will employ the information obtained from the bio-inventory toolbox to simulate and optimise several suitable biorefinery designs. The eventual goal of the decision support tool is to provide users with several optimised biorefinery designs that are tailored for their local setting. The additional toolboxes are detailed elsewhere.

Biorefinery Processing of Waste to Supply Cost-Effective and Sustainable Inputs for Two-Stage Microalgal Cultivation

Overcoming obstacles to commercialization of algal-based processes for biofuels and co-products requires not just piecemeal incremental improvements, but rather a comprehensive and fundamental re-consideration starting with the selected algae and its associated cultivation, harvesting, biomass conversion, and refinement. A novel two-stage process designed to address challenges of mass outdoor microalgal cultivation for biofuels and co-products was previously demonstrated using an oleaginous, haloalkaline-tolerant, and multi-trophic green Chlorella vulgaris. ALP2 from a soda lake. This involved cultivating the microalgae in a fermenter heterotrophically or photobioreactor mixotrophically (first-stage) to rapidly obtain high cell densities and inoculate an open-pond phototrophic culture (second-stage) featuring high levels of NaHCO3, pH, and salinity. An improved two-stage cultivation that instead sustainably used as more cheap and sustainable inputs the organic carbon, nitrogen, and phosphorous from fractionation of waste was here demonstrated in a small-scale biorefinery process. The first cultivation stage consisted of two simultaneous batch flask cultures featuring (1) mixotrophic cell productivity of 7.25 × 107 cells mL−1 day−1 on BG-110 medium supplemented with 1.587 g L−1 urea and an enzymatic hydrolysate of pre-treated (torrefaction + grinding + ozonolysis + soaking ammonia) wheat-straw that corresponded to 10 g L−1 glucose, and (2) mixotrophic cell productivity of 2.25 × 107 cells mL−1 day−1 on BG-110 medium supplemented with 1.587 g L−1 urea and a purified and de-toxified condensate of pre-treated (torrefaction + grinding) wheat straw that corresponded to 0.350 g L−1 of potassium acetate. The second cultivation stage featured 1H NMR-determined phototrophic lipid productivity of 0.045 g triacylglycerides (TAG) L−1 day−1 on BG-110 medium supplemented with 16.8 g L−1 NaHCO3 and fed batch-added 22% (v/v) anaerobically digested food waste effluent at HCl-mediated pH 9.

Multicriteria Definition of Small-Scale Biorefineries Based on a Statistical Classification

Biorefineries have many possible designs and therefore, present varied benefits in regards to sustainable development. Evaluating these biorefineries is central for the domain, and, as small-scale biorefineries (SSB) are commonly opposed to the large ones, specifying the concept of scale of a biorefinery is essential as well. However, there is no consensual definition of the “scale”, and the meaning of the term changes with the context. This paper presents a methodology to specify the concept of scale by grouping various biorefineries processing lignocellulosic biomass according to factors related to feedstock, process, economy and mobility of the facility, without any predetermined pattern. Data from 15 operational biorefineries are analyzed using a multivariate analysis combined with a hierarchical clustering. The classification obtained categorizes biorefineries into four design classes: smallest, small, hybrid and large scale. Small-scale biorefineries are characterized by a small investment cost (less than 2 M€), a low processing capacity (less than 100 t/day) and a low process complexity, while the end-products’ added value is variable. The mobility of the plants is a sufficient, but not necessary, criterion to have a small-scale biorefinery. Finally, the designs of the investigated biorefineries can be explained by two main trade-offs: one between the mobility and the processing capacity-investment cost, and the other between the process complexity and the added value.

Semi-refined Crambe abyssinica (Hochst. EX R.E.Fr.) oil as a biobased hydraulic fluid for agricultural applications

Vegetable oils are well known for their potential applications in green chemistry, including use as hydraulic fluids. Among oilseed crops, Crambe abyssinica Hochst. EX R.E.Fr . gained attention for its low-input requirements during cultivation and for the properties of its oil, characterised by a high erucic acid content. This long-chain mono-unsaturated fatty acid provides appreciable features that make the oil suitable for interesting green chemistry sectors, as biolubricants and cosmetics. In the present work, Crambe oil was tested as a hydraulic fluid for sustainable agricultural applications. Crambe oil was partially refined through phospholipid removal and added with a food-grade antioxidant (tert-butylhydroquinone) at two different concentrations. The fluid efficiency tests were carried out using an experimental test rig, able to simulate a real hydraulic device, performing heavy work cycles at 40-MPa pressure and at 100 °C temperature, with the aim of strongly accelerating the ageing of the tested fluid. At a lower antioxidant concentration, 0.25 g kg−1, the oil underwent a very quick degradation process. However, increasing the additive dose to 2.0 g kg−1, the fluid maintained stable performances. Indeed, all parameters, referred to oil chemical-physical stability and technical performance, were constant along the entire work cycle, up to 290 h. Finally, the present work showed how Crambe seed cultivation, oil extraction and exploitation in the hydraulic circuit of farm machinery could be developed applying green chemistry approaches aiming at small-scale biorefineries linked to the local supply.

Simulation Approach Through the Biorefinery Concept of the Antioxidants, Lignin and Ethanol Production using Olive Leaves as Raw Material

Olive leaves is derived from the olive oil production with limited practical applications. This raw material can be used to obtain added-value products through its processing applying the biorefinery concept. Therefore, The aim of this work is to evaluate from a techno-economic and environmental perspective the production of antioxidants, lignin and ethanol using olive leaves as raw material through the use of experimental data and process simulation. For this, a biorefinery scheme composed by an acid extraction stage, organosolv pretreatment and simultaneous saccharification and fermentation process was simulated. This process was performed using experimental data obtained from the main conversion blocks of the proposed scheme assuming a linear scaling. Moreover, the separation and purification of the products were performed using conceptual process design tools. Then, the techno-economic assessment was carried out considering economic indicators of the Spain context for an operating facility with a 10 y life-time. Finally, the environmental evaluation was based in the specific solid, liquid and gaseous emissions calculation. The results showed that 100 g of feedstock can produce 38.24 g of antioxidant extract (phenolic compounds>10 %), 11.82 g of lignin and 3.65 mL of bioethanol. In addition, the techno-economic assessment showed that the proposed biorefinery is profitable when 30,000 t/y are processed with a total project cost of 49.1 M USD, an internal rate of return of 15.22 % and a payout period of 7.27 y. As conclusion, the application of the biorefinery concept to upgrade olive leaves in added-value products is feasible from a techno-economic point of view and the implementation of small scale biorefineries in Jaen (Andalusia, Spain).

Integral use of plants and their residues: the case of cocoyam (Xanthosoma sagittifolium) conversion through biorefineries at small scale.

During last decades, there has been a growing interest of decreasing the environmental impact generated by humans. This situation has been approached from different perspectives being the integral use of raw materials as one of the best alternatives. It was estimated that 3.7 × 109tonnes of agricultural residues are produced annually worldwide. Then, the integral use of feedstocks has been studied through the biorefinery concept. A biorefinery can be a promissory option for processing feedstocks in rural zones aiming to boost the techno-economic and social growth. However, many plants produced at small scale in rural zones without high industrial use contribute with residues usually not studied as raw materials for other processes. Cocoyam (Xanthosoma sagittifolium) is a plant grown extensively in tropical regions. Nigeria, China, and Ghana are the main producers with 1.3, 1.18, and 0.9 milliontonnes/year, respectively. In Colombia, there are no technified crops, but it is used where it is grown mainly as animal feed. This plant consists of leaves, stem, and a tuber but the use is generally limited to the leaves, discarding the other parts. These discarded parts have great potential (lignocellulose and starch). This work proposes different processing schemes using the parts of the plant to obtain value-added products, and their techno-economic and environmental assessment. The simulation was performed with Aspen Plus and the economic package was used for the economic assessment. For the environmental assessment, Waste Algorithm Reduction of the U.S. EPA was implemented. The obtained results showed that the integral use of plants under a biorefinery scheme allows obtaining better techno-economic and environmental performance and that small-scale biorefineries can be a promissory option for boosting rural zones.

Alternatives of Small-Scale Biorefineries for the Integrated Production of Xylitol from Sugarcane Bagasse

Fil: Clauser, Nicolas Martin. Consejo Nacional de Investigaciones Cientificas y Tecnicas. Centro Cientifico Tecnologico Conicet - Nordeste. Instituto de Materiales de Misiones. Universidad Nacional de Misiones. Facultad de Ciencias Exactas Quimicas y Naturales. Instituto de Materiales de Misiones; Argentina

Unraveling Dutch citizens’ perceptions on the bio-based economy: The case of bioplastics, bio-jetfuels and small-scale bio-refineries

Little is known about how citizens perceive the transition towards a bio-based economy (BBE), despite the fact that they are one of the most important actors in this transition. Citizens’ perceptions of bio-based innovations can support policy-makers to improve the quality of decision-making and the bio-based industry to develop innovations. This study explores Dutch citizens’ arguments for and against three selected bio-based innovations: bioplastics, bio-jetfuels and small-scale bio-refineries. Randomly selected Dutch citizens were consulted in seven focus groups discussions (n=57). Results show that participants generally favor the contribution of bio-based technologies to economic growth and sustainability, but also mentioned several negative effects, such as high costs, food shortages or deforestation. In forming their opinion, citizens carefully weigh pros and cons of bio-based technologies from the perspective of their own interests and context, and this varies per bio-based technology. Their acceptance and support towards bio-based technologies increases when they feel more engaged with these technologies, and becomes even stronger when they identify opportunities for direct personal benefits, as in the case of the small-scale bio-refinery. This acceptance and support reduces if another important value is threatened (e.g. accessible mobility in the case of bio-jetfuels). Reliable information on both the advantages and disadvantages of bio-based technologies, coming from a neutral and independent body, is necessary in order for citizens to make their own judgments.

Sodium Bicarbonate Pretreatment on Rice Straw for Bioethanol Production and Utilizing the Waste Water of this Process to Absorb CO2 in Biogas.

The concept of small scale biorefinery from lignocellulosic biomass demonstrated the efficiency of energy and environment through research works at a pilot plant of University of Technology, VNU-HCM. The concept focused on studying bioethanol production in which pretreatment is one of key steps to achieve the efficiency. The pretreatment using NaOH solution 1.0 wt % removed lignin effectively but it is not considered as an eco-friendly chemical. Therefore, this study aims to investigate the alkaline pretreatment using Sodium Bicarbonate (NaHCO3), which is argued to be more environment-friendly and quite cheap. A variety of different conditions were investigated to optimize the pretreatment, including concentration of Sodium Bicarbonate (2.0-8.0 wt%), rice straw content (2.5-10.0 wt%), reaction temperatures (from room temperature to 80oC) and soaking time (4h-32h). The optimized condition was also investigated in combination with ultrasound and stirrer. The results showed that sodium bicarbonate is of quite potential to be used in the rice straw pretreatment. In addition, the waste of water from pretreatment was utilized to absorb CO2 in Biogas which was obtained from Thai My Demonstration plant in Cu Chi District.

Comparing alternative cellulosic biomass biorefining systems: Centralized versus distributed processing systems

This study explores how two different cellulosic ethanol production system configurations (distributed versus centralized processing) affect some aspects of the economic and environmental performance of cellulosic ethanol, measured as minimum ethanol selling price (MESP) and various environmental impact categories. The eco-efficiency indicator, which simultaneously accounts for economic and environmental features, is also calculated. The centralized configuration offers better economic performance for small-scale biorefineries, while the distributed configuration is economically superior for large-scale biorefineries. The MESP of the centralized configuration declines with increased biorefinery size up to a point and then rises due to the cost of trucking biomass to the biorefinery. In contrast, the MESP in the distributed configuration continuously declines with increasing biorefinery size due to the lower costs of railroad transportation and the greater economies of scale achieved at much larger biorefinery sizes, including biorefineries that reach the size of an average oil refinery—about 30,000 tons per day of feedstock. The centralized system yields lower environmental impacts for most impact categories than does the distributed system regardless of the biorefinery size. Eco-efficiency analysis shows that the centralized configuration is more sustainable for small-scale biorefineries, while the distributed configuration with railroad transport is more sustainable for large-scale biorefineries. Compared with gasoline from petroleum, cellulosic ethanol fuel offers sustainability advantages for the following environmental impact categories: fossil energy consumption, global warming, human health impacts by particulate matter, ozone layer depletion, ecotoxicity, human health cancer, and human health non-cancer, depending somewhat on the biorefinery sizes and the system configurations.

Energy Balance of Small-scale Biorefinery System

Energy Balance of Small-scale Biorefinery System

Media roundtable: DOE investment into small-scale biorefineries

Media roundtable: DOE investment into small-scale biorefineries