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Third-generation biofuel produced from microalgae is a viable solution to global energy insecurity and climate change. Despite an annual current global algal biomass production of 38 million litres, commercialization confronts significant economic challenges. However, cost minimization strategies, particularly for microalgae cultivation, have largely been excluded from recent studies. Therefore, this review provides essential insights into the technologies and economics of cost minimization strategies for large-scale applications. Cultivation of microalgae through aquafarming, in wastewater, or for biogas upgrading, and co-production of value-added products (VAPs) such as photo-bioreactors, protein, astaxanthin, and exopolysaccharides can drastically reduce biodiesel production costs. For instance, the co-production of photo-bioreactors and astaxanthin can reduce the cost of biodiesel production from $3.90 to $0.54 per litre. Though many technical challenges need to be addressed, the economic analysis reveals that incorporating such cost-effective strategies can make the biorefinery concept feasible and profitable. The cost of producing microalgal biodiesel can be lowered to $0.73kg−1 dry weight when cultivated in wastewater or $0.54L−1 when co-produced with VAPs. Most importantly, access to co-product markets with higher VAPs needs to be encouraged as the global market for microalgae-based VAPs is estimated to rise to $53.43 billion in 2026. Therefore, policies that incentivize research and development, as well as the production and consumption of microalgae-based biodiesel, are important to reduce the large gap in production cost that persists between biodiesel and petroleum diesel.

About a million Rohingyas have fled due to the ethnic cleansing in Myanmar and sought refuge in Bangladesh. The refugees are located in temporary settlements on hilly areas of Cox’s Bazar with inadequate water and sanitation facilities, giving rise to diseases such as cholera, typhoid, and diarrhea. This exploratory study reports drinking water security challenges in two Rohingya refugee camps within the larger camp network—Camp 2 and the recently-built Camp 4 Extension (Camp 4Ext)—to discover the key everyday issues refugees are facing related to drinking water. Both qualitative and quantitative methods have been applied to determining whether contamination is occurring during the collection, transportation, and storage of drinking water by comparing the water quality at the source with that in storage. The results show that Camp 4Ext is more suited for living in several respects compared with the other camps, attributable to significantly better planning during its construction: there is a lower prevalence of diseases, lower water collection times, higher standards of sanitation, and better access to water sources. This study’s outcomes will help camp authorities and the various agencies working there to provide sustainable water and sanitation interventions to improve the wellness of the Rohingya refugees in Cox’s Bazar. The outcomes will also provide useful information and strategic direction to the global scientific and development communities who are working in refugee camps in other parts of the world, to tackle water security challenges.

Biogas production is rising in the context of fossil fuel decline and the future circular economy, yet raw biogas requires puri-fication steps before use. Here, we review biogas upgrading using physical, chemical and biological methods such as water scrubbing, physical absorption, pressure swing adsorption, cryogenic separation, membrane separation, chemical scrubbing, chemoautotrophic methods, photosynthetic upgrading and desorption. We also discuss their techno-economic feasibility. We found that physical and chemical upgrading technologies are near-optimal, but still require high energy and resources. Biological methods are less explored despite their promising potential. High-pressure water scrubbing is more economic for small-sized plants, whereas potassium carbonate scrubbing provides the maximum net value for largesized plants.