Holistic farming systems provide designs for the whole farm that make long term sustainable use of nutrients, water, labour, finances and energy. In using organic residues to produce energy, and safely recycling the digested residues back into the farming system, a biogas digester could be a central component of many holistic systems. This paper discusses the influence of environmental, socioeconomic and cultural constraints on the use of biogas digesters in holistic farming systems in Sub-Saharan Africa. In higher altitude areas where maintenance of optimal temperature can constrain anaerobic digestion, floating drum or fixed dome digesters are a better option than flexible balloon digesters because they are less susceptible to temperature changes. If water is a key constraint, rainwater harvesting could be used to reduce the additional labour needed to collect water. If energy is the most limiting resource in the farming system, the optimum use of organic residues might be as a fuel for anaerobic digestion, whereas, if water is limiting, energy production by burning or pyrolysis might be a better option. The bioslurry from anaerobic digestion can be used in fish ponds to produce plankton to feed fish, and can be applied to fertile fields and fields of intermediate fertility, while biochar from pyrolysis is better used to improve the soil in infertile fields. If labour is limiting, it is particularly important that the system design minimises any additional labour needed to process the organic residues on a daily basis, considering trade-offs between labour and other resources.
The Marchantiophyta (liverworts) are rich sources of phenolic substances, especially cyclic and acyclic bis-bibenzyls, which are rare natural products in the plant kingdom, together with bibenzyls and characteristic terpenoids. At present, more than 125 bis-bibenzyls have been found in liverworts. They are biosynthesized from the dimerization of lunularic acid via dihydrocoumaric acid and prelunularin. The structurally unusual cyclic and acyclic bis-bibenzyls show various biological activities such as antimicrobial, antifungal, cytotoxic, muscle relaxation, antioxidant, tubulin polymerization inhibitory, and antitrypanosomal activities, among others. The present review article deals with the distribution and structure of bis-bibenzyls, bibenzyls, and several characteristic entsesqui-and diterpenoids in liverworts. Furthermore, the biosynthesis and total syntheses and biological activities of bis-bibenzyls are also surveyed.
This transdisciplinary literature review paper aims at addressing the literature lacuna in community engagement and water, sanitation and hygiene (WASH) in sub-Saharan countries. By responding to a set of identified WASH-related questions to community engagement, it explores through different disciplinary lenses the challenges and opportunities in this significant area that impacts human health. This transdisciplinary review brought together the disciplines of water engineering, environmental microbiology, public health and infectious disease, design research, women and gender studies, and developmental studies. It examined over 430 papers with 29 papers included in the final review. The main findings suggest integrating women into leadership roles in community water management and water and sanitation programmes can lead to more sustainability and can make water projects more effective. Second, cultural preferences should be a key factor when planning and implementing WASH technologies and interventions. Third, for community engagement to be effective, it should be done with intentionality and over a longer period; and employ existing culturally embedded leadership structures, such as schoolteachers, religious leaders and train change agents.
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