Assessment Of Emerging Contaminants In Compost And The Factors Influencing Compost Adoption In Ghana

Abstract

Waste and soil management remain a critical environmental concern in many African cities, including Accra (Ghana), even though most of these wastes are biodegradable and compostable. With these challenges and prospects, compost adoption will help close the organic matter and nutrient cycle gap. However, compost comes with challenges, including adoption and contaminants issues. With progressive industrialisation and technology, emerging contaminants (ECs) could be present in compost, potentially affecting the environment and human health. Therefore, this study aimed to understand the risk of ECs in compost, the potential uptake of ECs in compost by plants (lettuce and carrot) and studying the factors influencing compost adoption. Here, this study involved three ECs (pesticides, PAHs and antimicrobial drugs) from three waste sources [mixed waste municipal solid waste (MWMW), source-separated municipal solid waste (SSMW) and municipal and agricultural solid waste (MAW)]. This study used the compost’s maximum concentration of ECs to assess risk by comparing it with known ecological and human health criteria and identifying contaminants of potential concern (CPC). Also, the study predicted the optimum concentration of ECs in soils and the maximum risk quotient (RQ max) with two compost application rates [10 t/ha and 5 t/ha]. As there was no criterion for some quantified ECs, this research involved planting lettuce and carrot to identify the potential uptake and translocation of ECs with compost of known EC quantities. The study also examined the views of 350 farm-owners from Accra’s key farming locations on compost adoption using structured questionnaires, focus group discussions, and key informants’ interviews. The methodology involved descriptive statistics and probit analysis using an eleven-variable (biophysical and socio-economic) regression model to explain the key factors (including socio-cultural) influencing compost adoption. Further, there was an interaction within the predictor variables to evaluate their effect on adoption. Of the targeted 49 pesticides, the study quantified glyphosate, atrazine, triclopyr, chlorpyrifos and lambda-cyhalothrin. The rests were methoxychlor, cyfluthrin, and hexachlorocyclohexane (HCH) isomers. These isomers were beta-HCH, gamma-HCH and delta-HCH. Thirteen (13) out of the 16 US EPA priority PAHs from the waste sources. They included acenaphthene, acenaphthylene, fluorene, anthracene, fluoranthene, chrysene, benzo(a)anthracene, and pyrene. The rest were phenanthrene, benzo (b) fluoranthene, benzo (a) pyrene, benzo[g,h,i]perylene and Indeno(1,2,3,c,d)pyrene. The antimicrobial residues identified included; amoxicillin trihydrate, danofloxacin mesylate, sulfadiazine, ciprofloxacin hydrochloride and amprolium hydrochloride. Two drugs (danofloxacin and ciprofloxacin) were in the compost samples. There was a drastic reduction in the compost, confirming the effectiveness of composting in treating antimicrobial residues. The maximum concentration of identified ECs (pesticides, PAHs and antimicrobial drugs) was within the ecological criteria (0.004mg/kg) except for the three isomers of hexachlorocyclohexane. The maximum residue of gamma-HCH, beta- HCH, and delta-HCH recorded in the composts were 0.024, 0.028 and 0.049 mg/kg, respectively. The maximum predicted soil residues of ECs after composts applications at 5 t/ha ranged from 0.0001 mg/kg for beta-HCH and gamma-HCH to 0.0002 mg/kg for delta-HCH. At 10t/ha of the composts, the maximum predicted soil concentrations were 0.0002 mg/kg for gamma-HCH and beta-HCH and 0.0004 mg/kg for delta-HCH. All the compounds had an RQ max of less than 1; therefore, these ECs were low priority. Regardless of the compost’s content of ECs, the vegetable analysis showed pesticides, PAHs and antimicrobial drugs uptake from the compost treatments during the study period. There were ECs in the compost, and no ecological or health risk was associated with compost. No uptake and translocation of contaminants by plants (lettuce and carrot). The study recommended continuous monitoring of these contaminants in compost and food. The social survey findings showed that, although compost was available, the adoption rate was low (16%), mainly due to cost. Household size, per-capita income, and compost-specific training for farmers had a significant positive effect on adoption, while the farmers’ age had a significant negative impact. A multivariate interaction between age and compost-specific training positively impacted adoption. Also, age and education showed a high possibility of the farmer adopting compost. As farm and household size increased, the farmer was more likely to adopt compost with a higher adoption rate. However, as age and farm size increase, the farmer is less likely to use compost. Male farmers who had received training were less likely to adopt compost than their female counterparts, and males with enormous households were not likely to adopt compost. It appears the male farmers were complacent regarding their attitude toward compost adoption irrespective of receiving training, increased household size or increased per capita income. Biophysical and socioeconomic factors affected compost adoption. Policymakers should involve female farmers by giving them compost-specific training without neglecting the males.