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.

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.

It is a truism by now that the combustion of fossil fuels has execaerbated climate change, and its repercussions. Biomass in pelletised form, will emerge as substitutes, in the circular bioeconomies of the future. This brief review focuses on the utilisation of agricultural residues as raw materials for pellets, and explores the aspects of sustainability – socio-cultural, economic, environmental, and techno-functional – in the 20-plus peer-reviewed articles selected for that purpose using Scopus with a set of search-phrases. The articles are case studies dated between 2012 to 2023, tracing their provenance to different countries in the world – Brazil, Canada, China, Denmark, Greece, India, Italy, Mexico, Peru, Spain, Thailand, Türkiye , Zambia, etc. Among the many gleanings which are reported in this review, some deserve mention here in the abstract. The social aspect of sustainability has not been studied as much as the economic and environmental. The case studies emphasize the importance of adapting the pelleting process to the properties of the agricultural/horticultural residues and the prevalent local conditions. It is encouraging to note that there is a surfeit of agricultural residues (corn, coffee, quinoa, beans, oats, wheat, olives, tomatoes, pomegranates, grapes, etc. in the articles reviewed) which can be valorised to pellets, also in combination with the in-vogue forestry wastes. This is all the more advisable if the status quo is open burning of such residues in the fields. The journey towards the sustainable development goals (SDGs) will be aided by investments in such biorefinery-projects, SDG 17 is extremely vital for their success – collaboration and cooperation among several stakeholders around the world. This review, though based on only 20-plus articles from around the world, is an indepth analysis which promises to be of interest to decision-makers and sustainability-specialists keen on contributing to the transition to a circular bioeconomy.

‘Zoo-ethics’is a subset of bioethics,and zoology may be looked upon as a subset of ecology...that is how the review of Survival at Stake, by Poorva Joshipura, falls well and truly within the scope of this journal.There is also an interesting link between this one and another review of a book steeped in science, published recently by this author. Survival at Stake, on the other hand, primarily, has a moral, ethical, and practical force embedded within the scientific. This is understandable when one notes that Joshipura is an animal welfare activist associated with the NGO, People for the Ethical Treatment of Animals (PETA), and committed to the cause espoused by it.

Zimbabwe has diligently started pursuing the Sustainable Development Goals (SDGs) defined by the United Nations in 2015. While making progress and being aware of it, will be a shot in the arm, with success breeding more success, the journey may seem daunting at times. However, the journey –sustainable development towards the targets set -is what matters morethan the final destination, as philosophers and savants often remind us. This article, while dwelling on sustainable development in this southern-African landlocked country in general, presents a beautiful example of a collaborative venture, undertaken by dedicated and determined international partners, and predicated on SDG#4 (Quality Education) and SDG#5 (Gender Equality), and harnessing the complementarities and synergies with the other SDGs, which set root during the COVID-pandemic, in Mwenezi in southern Zimbabwe. The pandemic while being a scourge, tended to have some silver linings to it, as it gave birth to many collaborationsand made human beings realise that one’s own happiness is dependent to a very great extent on that of others. This venture emphasizes girls’ educationand skills-development, which open the doors, synergistically, to sustained growth, development and progress. Education, indisputably, is a key component of the freedom necessary to live a life of value. To quote Nelson Mandela, ‘It is the most powerful weapon which you can use to change the world.

The Varshita Venkatesh Written-Word Workshop set up by the author in honour and memory of his wife Varshita,who ascended to her heavenly home in January 2020, can be labelled as a ‘no-income-to-entrepreneur’ socialentrepreneurship construct which knits together a swathe of different stakeholders to the ‘Varshita Venkatesh family ofcharitable funds’, so to say, and uncovers and creates value of different types—economic, social, spiritual, psychologicaland moral. It has a long way to go, in this ‘value-creating’ journey and contribute to sustainable development in its ownhumble way

Carmine Gallo packs a punch and makes this book as novel and memorable as a top-class TED talk.