Water hyacinths are becoming a problem in lakes, ponds and waterways in many parts of the world. This paper contains a literature study of different ways to use water hyacinths, mainly in agricultural or alternative energy systems. The literature review indicated that water hyacinths can be rich in nitrogen, up to 3.2% of DM and have a C/N ratio around 15. The water hyacinth can be used as a substrate for compost or biogas production. The sludge from the biogas process contains almost all of the nutrients of the substrate and can be used as a fertiliser. The use of water hyacinth compost on different crops has resulted in improved yields. The high protein content makes the water hyacinth possible to use as fodder for cows, goats, sheep and chickens. Water hyacinth, due to its abundant growth and high concentrations of nutrients, has a great potential as fertiliser for the nutrient deficient soils of Africa and as feed for livestock. Applying the water hyacinths directly without any other processing than sun drying, seems to be the best alternative in small-scale use due to the relatively small losses of nutrients and workload required. To meet the ever-growing energy demand, biogas production could be one option but it requires investments and technological skills that would impose great problems in developing countries where the water hyacinth is often found. Composting as an alternative treatment has the advantage of a product that is easy to work into the soil compared with dried water hyacinths, because of the decomposed structure. Harvesting and transport of water hyacinths can be conducted manually on a small scale and does not require a new harvesting technique to be introduced. Transporting of fresh water hyacinths means, if used as fertiliser in amounts large enough to enhance or effect crop growth, an unreasonably large labour requirement. Based on the labour need and the limited access to technology, using dried water hyacinths, as green manure is a feasible alternative in many developing countries. (c) 2006 Elsevier Ltd. All rights reserved.
Waste management policies aim to divert waste from lower positions on the waste hierarchy such as landfill and incineration to higher positions in the hierarchy such as energy recovery and recycling. However, empirical evaluations of such policies are scarce. This study highlighted the effect of waste management policies on the amount of waste treated with landfill, incineration, energy recovery and recycling by analysing a panel dataset consisting of 14 European countries and the period 1996 to 2018. Findings from a seemingly unrelated regression model suggest that the landfill ban is associated with a decrease in landfill waste, but an increase in incineration, energy recovery and recycling waste. The landfill tax is also correlated with an increase in energy recovery waste but, in contrast, it is associated with a reduction in incineration and recycling waste. Meanwhile, the deposit refund scheme is associated with a decrease in the amount of landfill waste. Concerning the effects on total waste generated, regression results from a fixed effects model indicate that the landfill tax and the deposit refund scheme are both correlated with a reduction in the amount of waste generated. These findings contribute to the scarce academic literature evaluating waste management policies and may better inform policy makers on their longer-term implications.