An Evaluation of Process Factors Affecting Water Hyacinth Based Bio Briquettes Production

ABSTRACT: Water hyacinth (Eichhornia crassipes) is a highly invasive aquatic weed that degrades freshwater ecosystems and creates severe socioeconomic burdens. This study addresses the dual challenge of invasive weed management and lack of affordable clean cooking fuel by converting water hyacinth biomass into high-quality bio-briquettes as a sustainable alternative to firewood and charcoal. The knowledge gap addressed is the lack of systematic, multi-factor optimization for water hyacinth briquetting under Southern African conditions, as well as the limited quantification of environmental benefits. Fresh water hyacinth was collected from Lake Chivero, Zimbabwe, characterized, and processed using a manual compression method. Sixteen process factors, including particle size, compression pressure, and moisture content, were systematically investigated. Raw water hyacinth exhibited 88.5% moisture, 65.2% volatile matter, 12.8% ash, 15.6% fixed carbon, and 14.2 MJ/kg calorific value. Water hyacinth-based briquettes were produced using 2–5 mm particles, 12–15% moisture, 10% maize starch binder, and 7 MPa compaction pressure, achieving 16.8 MJ/kg calorific value, 850 kg/m³ density, and 94.5% durability. Carbonized briquettes reached a calorific value of 24.5 MJ/kg. Environmental assessment showed harvesting removed 2.5 kg nitrogen and 0.5 kg phosphorous per ton of fresh biomass, increased dissolved oxygen from 3.2 to 5.8 mg/L, and avoided 0.12 kg CH₄ per kg dry biomass. The briquettes were 70% cheaper than charcoal and produced 45% less carbon monoxide and 67% less particulate matter than firewood. This study demonstrates that water hyacinth bio-briquettes offer a viable, low-cost, and environmentally beneficial solid fuel for rural communities while simultaneously addressing invasive weed management.