The transition from a fossil-based economy to a circular bioeconomy is a critical challenge and opportunity in the face of global climate change. Sweden and Finland, with their abundant forest resources and strong commitment to sustainability, are well positioned to lead this transition. The WoodPro project exemplifies this effort by exploring innovative ways to valorize forest residues into high-value products such as 2,3-butanediol (2,3-BDO), biopolymers and hydrochar. This perspective outlines the project’s multidisciplinary approach, which integrates advanced bioprocessing technologies with dynamic system analysis to optimize the sustainability and economic feasibility of these biorefining pathways. We highlight the potential of these interconnected processes to reduce greenhouse gas emissions, close nutrient loops and stimulate rural development, while positioning the Nordic countries as global leaders in the circular bioeconomy. The insights gained from this project highlight the importance of holistic, systems-based approaches in achieving carbon neutrality and offer a model for similar transitions worldwide.

The circular bioeconomy can be visualized as a set of ‘many through many to many’ relationships, connecting different types of biomaterials from a variety of source-sectors via diverse processes and technologies in biorefineries, to end-use applications availing of the resulting valorized bio-products. One end-use sector is the energy sector; the end-use applications being as sources of heat and electricity, and as transport fuels. The focus of the chapters in this book is on bioenergy and biofuels in a circular bioeconomy, while this introductory chapter is an overview of published research in this niche area

The circular bioeconomy can be visualized as a set of “many-through-many-to-many” relationships. It connects different types of biomaterials from a variety of source-sectors via diverse processes and technologies in biorefineries, to end-use applications availing of the resulting valorized bio-products. One end-use sector is the energy; the end-use applications being as sources of heat and electricity, and as transport fuels. The focus of the chapters in this book is on bioenergy and biofuels in a circular bioeconomy, while this introductory chapter is a very brief overview in this niche area. © 2025 Elsevier Ltd. All rights are reserved including those for text and data mining AI training and similar technologies.

Air pollution has become a scourge to contend with in India. The recorded concentrations of particulate matter (PM) in the atmosphere, the unabated emission of pollutants from vehicular exhausts, and recurring episodes of extremely poor condition (AQI>300) in the winter months, have rightfully and necessarily, spurred efforts in the industrial, governmental and research spheres to alleviate its detrimental impacts. Various point sources like biomass burning, coal combustion for power generation, and traditional agricultural practices such as stubble burning, collectively contribute to a steady rise in ambient particulate matter (PM) pollution. This study focuses on the utilization of rice straw – an abundant agricultural residue in a country like India – motivated by promoting and contributing to the soil-to-soil circularity paradigm. It encompasses the characterisation of straw ash from the rice, by delineating its physical properties, thermal characteristics, and chemical composition with the help of Thermogravimetric analysis (TGA), X-ray diffraction (XRD), Electron Probe Microanalysis (EPMA), Scanning Electron Microscopy (SEM), Transmission Electron Microscopy (TEM) and Dynamic Light Scattering (DLS). The results indicate that rice straw ash (RSA) possesses high silica content and favorable thermal stability. The RSA exhibited a porous structure, which enhances nutrient adsorption and microbial activity. Its incorporation into soil significantly improved soil nutrition and health, promoting a more sustainable agricultural practice. Entrenching this soil-to-soil thinking will contribute directly and indirectly to a host of sustainable development goals in a future Indian circular bioeconomy.

At Biogasbolaget AB in Karlskoga in south-central Sweden, organic wastes like food waste, manure, and silage are digested anaerobically to yield biogas, which subsequently can be upgraded to biomethane, and used as a replacement for fossil-diesel in public transport. The digesters at the firm are currently operating below their maximum capacity. This chapter deals with the evaluation of the potential of hydrochar to augment biogas production in a batch process. Hydrochar produced from two sources – forestry sector and municipal organic wastes – were compared, and using the Automatic Methane Potential Testing System (AMPTS II) in the lab at Karlstad University, the optimal dosage was determined. Experiments were also conducted with hydrochar alone, to verify if the hydrochar was being anaerobically digested to yield biogas. The hydrochar sourced from municipal waste, when dosed at 8 g/l, produced 841 Nml of biogas /gram of VS (volatile solids) in the substrate, 93% greater than the reference case of no addition of hydrochar. The forestry-sector-sourced hydrochar on the other hand, at the same dosage, registered an increase of just 16.6%. A streamlined environmental life-cycle analysis showed that significant climate-benefits can be availed of, implying environmental sustainability, when the additional biogas is refined and used to replace fossil-diesel in public bus transport. Hydrochar-assisted anaerobic digestion of organic wastes may be posited as a technology which may entrench itself in the circular bio-economies of tomorrow, around the world, and bywhile doing so, contribute to a set of sustainable development goals. While these were batch-digestion experiments, this part of the two-part series recommends more-realistic continuous-digestion experiments which incidentally form the focus of Part 2.

In the Part I of this two-part series, the potential of hydrochar of two different provenances to augment biogas production in a batch process, was evaluated, using the Automatic Methane Potential Testing System (AMPTS II) in the lab at Karlstad University. In Part 2 of the two-part series, this part, single-stage anaerobic co-digestion in two continuously-fed reactors, replaced the batch process of Part 1. A The possibility of connecting an existing digester with a hydrothermal carbonization (HTC) reactor was investigated, and a life-cycle costing analysis was carried out to determine if, in addition to the environmental benefits written about in Part I, investing in an HTC system to produce hydrochar in-plant to augment biogas production will be economically feasible. Hydrochar addition resulted in a 59% rise in biogas yield (and 53.5% in methane yield). The pH remained stable around 7.6 throughout the digestion process. The study confirmed It will be the techno-economic feasibility for coupling an ally practical and feasible to interconnect an HTC plant with a digester supplying 25% of the digestate it produces, to the former, as the raw material for hydrochar production. The rest of the digestate (rich in carbon, nitrogen and phosphorus) can find use as fertiliser. Investing in an The LCC analysis showed that investing in an HTC plant contributing to a rise in methane production of 17% (or 53%), will result in a net profit of 363 million SEK (or 1237 million SEK) over a 20-year period. If the Karlskoga biogas plant decides to rely on purchasing hydrochar from the external market instead, the corresponding net profit will be 177 million SEK (or 1052 million SEK) over the same 20-year period, implying that a decision to integrate and interconnect is likely to be economically more feasible, in a circular bioeconomy in the future.

This chapter deals with the modeling and analysis of a proposed industrial symbiotic system in Karlstad (Sweden), involving algal cultivation, a combined heat and power (CHP) plant and a wastewater treatment plant (WWTP). It has been organized into two parts—the first one focusing on the modeling and the second one, on the application of the model and an energetic and environmental analysis performed using the model developed in the first part. The focus is on the actual symbiotic relationship, the associated flows of materials and energy, and the environmental performance of the symbiotic system, located in Karlstad. In the proposed symbiosis, exhaust gases from the CHP are used as a source of carbon dioxide for the photosynthetic algae (which in the process double up as carbon sinks) as well as a source of heat for drying the harvested algal biomass. Recovered waste heat is used to maintain an appropriate temperature in the cultivation pond and the nutritional needs (nitrogen and phosphorus) of the algae are fulfilled by circulating digestate water from an anaerobic digester at the WWTP. Two possible scenarios for bioenergy recovery (from the algae) were studied—anaerobic digestion (scenario A) and direct combustion in the CHP (scenario B). The outcome is encouraging and shows that algae can be cultivated at the location of the CHP plant in Karlstad, over a longer period of time, vis-à-vis a stand-alone system, and thereby the average daily output can be augmented from 14 to 18g/m2. From an environmental point of view, scenario B fares better than scenario A. The integrated system has a net energy ratio of 2.6 for scenario A; and 5.3 for scenario B. The model and the analysis based on it clearly show that there are excellent opportunities for cultivating algae for use as biofuel locally in Karlstad, which can be harnessed by resorting to industrial symbiosis. A full-scale, detailed life cycle environmental analysis focusing on a range of environmental impact categories can be carried out in the future.

This chapter deals with the modelling and analysis of a proposed industrial symbiotic system in Karlstad (Sweden), involving algal cultivation, a combined heat and power (CHP) plant and a wastewater treatment plant (WWTP). It has been organized into two parts – the first one focusing on the modelling, and the second one, on the application of the model and an energetic and environmental analysis performed using the model developed in the first part. The focus is on the actual symbiotic relationship, the associated flows of materials and energy, and the environmental performance of the symbiotic system, located in Karlstad. In the proposed symbiosis, exhaust gases from the CHP are used as a source of carbon dioxide for the photosynthetic algae (which in the process double up as carbon sinks) as well as a source of heat for drying the harvested algal biomass.  Recovered waste heat is used to maintain an appropriate temperature in the cultivation pond and the nutritional needs (nitrogen and phosphorus) of the algae are fulfilled by circulating digestate water from an anaerobic digester at the WWTP. Two possible scenarios for bio-energy recovery (from the algae) were studied - anaerobic digestion (Scenario A) and direct combustion in the CHP (Scenario B).  The outcome is encouraging and shows that algae can be cultivated at the location of the CHP plant in Karlstad, over a longer period of time, vis-à-vis a stand-alone system, and thereby the average daily output can be augmented from 14 to 18 g/m2. From an environmental point of view, Scenario B fares better than Scenario A. The integrated system has a net energy ratio (NER) of 2.6 for Scenario A; and 5.3 for Scenario B The model and the analysis based on it clearly show that there are excellent opportunities for cultivating algae for use as biofuel locally in Karlstad, which can be harnessed by resorting to industrial symbiosis. A full-scale, detailed life-cycle environmental analysis focusing on a range of environmental impact categories can be carried out in the future.

Abstract: The water-, and energy footprints of the processes in the pulp and paper industry are sizable enough to warrant investment of money and commitment of time truncate the same. Besides, there is also a nexus between water and energy here, with optimisation of the use of one of these resoruces enabling that of the other too. This streamlined review focuses on journal publications (originating from different parts of the world, and targeted at researchers and decision-makers in the industry) which train the lens on the optimisation of water use in this particular sector of the (forestry) bioeconomy. The synergies and complementarities which exist among different sustainable development goals (SDGs) , promise positive ripple effects, caused by attending to the truncation of the water footprint. The articles, in general, recommend effective in-plant wastewater treatment in combinaton with recirculating the treated effluent, and looking upon the water streams as carriers or bearers of valorisable substances – organics which can yield a host of bio-products in bio-refineries, including bio-energy. Availing of water-pinch analysis as a tool to uncover possibilities of water use in a cascade (depending upon the requirements imposed on the water, by processes downstream in the cascade), has been shown to aid in the optimisation of both water use and energy demand within the plant. One case study, for example, showed that the demand for steam can be decreased by about 4 GJ per ton of output, by recovering the waste heat in the water streams. 

The supply-chain logistics – storage and transportation over long distances – and downstream processes in biofuel production are adversely impacted by the moisture content in the biomass feedstock. Most woody, herbaceous, low-cost biomass resources such as municipal organic solid wastes and forest residues have moisture content over 30% (of the wet-biomass mass). This makes them less amenable to thermochemical biomass-to-biofuel conversion technologies like pyrolysis and gasification. If pyrolyzed or gasified, the resulting biofuels have a higher moisture content, which truncates their calorific values. During storage, there is a loss of dry matter owing to a tendency to compost aerobically/anaerobically, which is detrimental to the quality of the biomass as a potential source of biofuel. Beyond that, fire hazards due to the spontaneous combustion of wet biomass are not uncommon, necessitating storage in a dry condition. However, drying high-moisture biomass is energy-intensive. The quality of the product and the efficiency of drying are affected by particle sizes and drying technologies adopted. Within this chapter, the authors focus on managing and controlling the moisture content of the biomass utilized in the biofuels sector by resorting to drying and torrefaction technologies. The chapter dwells on drying principles, models and media in drying systems, types of drying systems, mechanical dewatering and torrefaction, the impact of drying, dewatering, and torrefaction on the physical and chemical properties of the end-product, and techno-economic analysis of torrefaction.