Biosorption for Sustainable Small-Scale Gold Mining in Uganda

Project coordinator: Mary Therese Kaggwa

Coordinating institution: Kyambogo University

Partner institutions: University for Continuing Education Krems, Makerere University, Gulu University, University of Pretoria

Partner countries: Uganda, South Africa

Project duration:

Mercury-dependent artisanal and small-scale gold mining (ASGM) provides an important source of livelihood for several rural communities in Uganda (Esdaille and Chalker, 2018).  Between 400,000 and 600,000 people are directly employed through ASGM in Uganda, and another 2 million people are indirectly sustained by it. At least 45% of the workforce in ASGM are women and another 20% are children. Over 73% of Uganda’s artisanal gold is produced using toxic mercury (roughly 15 tons per year). In ASGM, gold is extracted from crushed rocks or soils through amalgamation with mercury. Through this practice, mercury is released into the environment during the evaporation of the amalgam (AuHg2) and unsafe disposal of the resultant tailings. Although alternative techniques have been proposed to replace mercury usage in ASGM, such methods are yet to be adopted in Uganda. The arable soils downstream of ASGM activities are prone to mercury contamination, yet the majority of rural communities depend on the same land for agriculture. Soil and water contamination is of great concern to Uganda because agriculture contributes significantly to the country’s GDP,  and Ugandans themselves largely consume locally grown products.

Growing food crops on contaminated soils exposes the population to mercury since plants and particularly predatory fish can accumulate this toxic metal (Ssenku et al, 2023). Fish and other flora and fauna in the surrounding waters and wetlands are also prone to mercury contamination. Indeed, results from a recent study conducted by Water Governance Institute, a local environmental organization found that soils, sediments, and food crops from ASGM areas in Uganda contain elevated levels of mercury (Karakire, 2021). Mercury poses serious health problems to humans including impaired cognitive function, neurological and kidney damage (Park et al., 2012). Thus, ASGM activities threaten the health of miners and communities around ASGM mines who consume mercury-contaminated foods.

The proposed project will combine principles of biosorption and chemical remediation to treat contaminated tailings, rehabilitate contaminated soils and protect vulnerable ecosystems surrounding ASGM areas in Uganda. This study will design biochar composites from locally available biomass to enhance mercury removal from tailings and limit its bioavailability in soils. During ASGM activities mercury is released into wastewaters and onto soils. Mercury is known to bind firmly with sulphur (S) containing ligands or groups and the strength of the coordination interaction depends on the nature of the S-group. In this respect, mercury solubility, mobility and bioavailability in various environmental systems can be influenced by the presence of S-bearing compounds (Leng et al., 2022). Biochar, depending on the conditions of production, can be made rich in S-bearing groups. Moreover, the S content can be enhanced through post-production treatment with S-containing biomass-derived materials or by S-doping during pyrolysis to increase the extent of sulphurization. In this respect, biochar composites loaded with S-groups can be utilized in trapping mercury from wastewaters and can also be optimized to retain mercury in soils and sediments, thereby arresting its mobility. The biosorbents will be tested in laboratory and field remediation of contaminated waters and soils.

The study will rehabilitate mercury-contaminated soils making them fit for agricultural production and contribute to food security. The study will also protect vulnerable ecosystems such as L. Victoria and wetlands. Moreover, the study will generate data on mercury transport and bioavailability in soils around ASGM areas which will help inform decision-making for policy makers. Further, the project will build capacity in environmental remediation and protection through the incorporation of acquired knowledge in MSc curriculum development in KYU, training young researchers and communities in ASGM areas. The biosorbent composites will be first tested in Namayingo (Eastern Uganda), Kasanda (Central Uganda), and Rubirizi (Western Uganda) areas. After the first phase, project activities will be rolled out to other ASGM areas in Uganda.

Importantly,   BioGold contributes  to the  realization of  APPEAR’s overall  objective  "strengthening  the  scientific foundation  and  institutional  capacities  in  higher  education and research and research for development in Uganda and partner countries", and aligns  APPEAR's  thematic  areas  of   protecting the environment  and sustainable management  of natural resources through enhancement of resource reclamation with use of bioremediation,  eradicating  poverty and meeting  basic needs especially water  and sanitation, achieving gender equality  and empowerment  of women  and children.

As highlighted earlier, ASGM employs significant numbers of women and children, especially at the extraction stage from the rocks. This shows that they are the most at risk as they have no protective gear and lack awareness of the dangers of the resultant effects of the chemicals they use in the process. BioGold proposes to work with these communities with a greater focus on these vulnerable groups by sharing knowledge from the research and sensitization of the communities on the associated challenges and how they can be mitigated to allow them to operate in a safe environment. Additionally, the BioGold collaboration is predominantly composed of women (57%) and headed by a woman. This seeks to enhance women’s empowerment in leadership, research and management.