This case study aims to identify the sources of natural and anthropogenic As and heavy metals (HMs) in biodegradable wastes to develop controls on waste properties for efficient operation of biochemical waste treatment systems and better end product quality. Biodegradable waste from different income levels was sieved into seven size fractions (B-MSW), acid digested and their metal content was determined by ICP-OES. The data on the level and loads of As and HMs in the waste were statistically investigated to identify their sources. Metals' concentrations were well correlated (p <= 0.001), and below established limits for thermal and biological processing of B-MSW. Metal sources identified in B-MSW linked to agricultural activities, constituting 68.1% of the total variance; soil geochemistry (25.5%) > phosphate fertilizers (20.3%) > agricultural chemicals (14.2%) > irrigation water (8.1%). The effect of solid fuel residues (11.3%), metals and plastics (7.5%) and Al-Mn alloy cans (6.3%) in mixed collected waste accounts for 25.1% of the total variance. Improvements in regulatory controls for protection of irrigation water quality and restrictions on the use of fertilizers and agrochemicals will reduce HM loads in the B-MSW. In addition, we recommended applying a source-segregated MSW collection to avoid cross-contamination of biodegradable materials to achieve high product quality and reduced emissions.