On the potential of water hyacinth as a biomass briquette for heating applications

Int J Energy Environ Eng (2016) 7:37–43 DOI 10.1007/s40095-015-0195-8 ORIGINAL RESEARCH On the potential of water hyacinth as a biomass briquette for heating applications K. Munjeri1 • S. Ziuku2 • H. Maganga1 • B. Siachingoma3 • S. Ndlovu4 Received: 13 April 2015 / Accepted: 7 October 2015 / Published online: 5 November 2015 Ó The Author(s) 2015. This article is published with open access at Springerlink.com Abstract This article highlights the environmental challenge posed by water hyacinth on fresh water sources in Zimbabwe and investigates the use of the harvested weed as a source of energy in the form of briquettes. The water hyacinth (Eichhornia crassipes), known to be native to South America, has now become an environmental and social challenge throughout most water sources in Zimbabwe. It adversely affects the environment and humans in diverse ways. However, the plant leaves and stem release thermal energy when burned. The amount of thermal energy released depends on the moisture content and other factors. The water hyacinth organic matter and other leaf species were briquetted and their thermal energy content investigated in this exercise. The thermal energy content of the various samples was measured using a bomb calorimeter. Results of the experiments showed that the calorific value of briquetted hyacinth was 14.55 MJ/kg. The calorific value of briquetted samples of other eleven leaf species ranged from 14 to 20 MJ/kg. Moisture content, volatile matter and ash content results of the samples are also reported in this paper. The results show that water hyacinth briquettes can be used as thermal and lighting & S. Ziuku ; 1 Department of Physics, University of Zimbabwe, Box MP167, Harare, Zimbabwe 2 Energy Technology Institute, SIRDC, Box 6640, Hatcliffe, Harare, Zimbabwe 3 Physics Department, Midlands State University, P. Bag 9055, Gweru, Zimbabwe 4 Bindura University of Science Education, P. Bag 1020, Bindura, Zimbabwe energy source particularly for communities staying in the vicinity of the affected water sources. Keywords Water hyacinth  Briquettes  Gross calorific value  Fixed carbon  Ash content Introduction The spread of the fast-growing water hyacinth weed in Harare’s Lake Chivero and other open water sources is threatening the capital city’s main water supply. Environmentalists blame the spread of the weed on the discharge of effluent, particularly raw sewage, into the Lake and its tributaries. The weed has spread, to many other water bodies throughout Zimbabwe. The plant grows rapidly and produces enormous amounts of biomass. Due to its flat top leaf structure, it covers extensive areas of open waterways. The water weed causes ecological and economic problems by impeding navigation, fishing and recreational activities. The weed’s rapid growth rate creates chronic shortage of dissolved oxygen required by the water’s fauna and the flora [1, 2]. Perna and Burrows [3] noted that the water hyacinth cover on water bodies reduces the gaseous exchanges that take place at the air–water interface and reduce the photosynthetic activity of submerged plants by hindering the penetration of the sun’s rays. Figure 1 shows the clogged Manyame river, one of the tributaries of Lake Chivero. In slow-moving water bodies, water hyacinth mats physically slow the flow of water, causing suspended particles to be precipitated, leading to siltation. The reduced water flow can also cause flooding and adversely affect irrigation schemes by clogging the canals and piping systems. Displacement of water by water hyacinth can mean 123 38 Int J Energy Environ Eng (2016) 7:37–43 Fig. 1 Water hyacinth on Manyame River that the effective capacity of water reservoirs is reduced by up to 400 m3 of water per hectare, causing water levels in small reservoirs to fall more rapidly in dry periods [4]. Methods for controlling the water hyacinth weed include manual and mechanical removal as well as chemical and biological interventions. Chemical use is the fastest but it has gross negative impact on the environment and water quality. The chemicals will also have to be removed to make the water safe for human consumption. Although it may be used in conjunction with other control methods, biological control is an essential option in any management plan to control the hyacinth water weed. Biological control is relatively cheap and safe for the environment giving long-term sustainable control with minimal maintenance once the weevil is established. The biological method is ideal for large areas, environmentally sensitive areas, sites where access is not possible for spraying or harvesting, sites susceptible to re-infestation and sites where water is being used for stock watering. The weevils will also disperse to other areas, including inaccessible or difficult terrain. With biological control, there is no danger of offtarget damage to, or removal of other desirable plants which can occur with herbicides or manual harvesting. However, biological control should not be used where eradication is to be attempted unless it is to thin out a large area prior to eradication. Eradication is rarely possible with biological control, and carries the danger that the insect population will die out, and the weed will then return. The ideal situation is to achieve a dynamic equilibrium where both the plant and the insect survive at low levels without causing economic damage [5]. Large-scale mechanical processes usually require machines powered by electricity or liquid fuels. This tends to increase the process costs and damage the environment. The manual process using handheld tools is slow considering the rate at which the water weed multiplies. Nevertheless, for the purposes of 123 productive plant utilisation, it is the best way to harvest the weed. It has been reported that water hyacinth weed cannot be used as stock feed because of low protein content. It cannot also be used to make paper because of its short stalk length. However, it can be utilised to remove heavy metals from sewage and as an energy source in the form of briquettes. Substantial research work has been directed towards searching for various ways of realising value in the weed. The weed is not only affecting water supply to cities and towns in Zimbabwe, but is also negatively affecting the livelihoods of people living close to the infested water bodies. These communities usually consist of the poor and vulnerable who have limited access to basic energy services. In most cases, they use wood and paraffin leading to deforestation, indoor pollution, and increased procurement costs. It is also worth noting that urban dwellers in Zimbabwe have also resorted to the traditional energy sources such as wood due to frequent electricity outages. The country’s sole utility, the Zimbabwe Electricity Supply Authority (ZESA) generates about 60 % of the Country’s peak demand and imports power from South Africa, Mozambique and Democrat (...truncated)