The recycling of fly ash, a product of coal burning, converts it from an environmental nuisance on land, to a beneficial factor in the sea. The State of Israel uses increasing quantities of coal to produce electric energy. The enormous quantities of fly ash (>10% of the burned coal) produced as a result of the utilization of such an energy source, have been directed in part to the cement industry. A considerable portion, however, remains unused. To date, more than a million cubic tons have been disposed of in the deep sea. The bulk disposal of fly ash in the deep sea is costly, due to the expense of marine transportation, and is undesirable from an ecological point of view. Recycling of the fly ash is beneficial economically and ecologically. One possible use for the ash is in the construction of artificial reefs and through them, the "afforestation of the sea".
It is not known how fly ash, consolidated using technologies currently known in Israel, or as a major component of marine concrete, will behave in the open sea conditions of the Mediterranean. A main concern is the secretion of dangerous materials into the sea. Laboratory experiments have indicated that the smaller the surface area of the fly ash (in a consolidated state), the less the probability of secretion. The Israel Ministry for the Environment is adamant that there be no heavy metals leaching into marine biota, thus contaminating our food through the food web. It is with this aim that The Israel Electric Company is supporting a study of these issues, conducted by the Leon Recanati Center for Maritime Studies. The research is headed by Ehud Spanier in cooperation with Moshe Tom and Nurit Kress from the Biology and Chemistry departments of the Israel National Institute of Oceanography. Duration of the research will be at least two years.
Eighty blocks, containing 0%, 40%, 60% and 80% coal fly ash from the Hadera Orot Rabin power plant, were prepared at the National Building Laboratory at the Technion, Israel Institute of Technology. Each block was weighed and tagged with an individual plastic number. Samples from each of the four concrete mixtures were tested for mechanical strength. The blocks were arranged randomly and attached in groups to chemically inert PVC frames. The frames were deployed in the open sea on the seabed, at a depth of 19 m (in the general vicinity of the Center for Maritime Studiesí artificial reefs).
The biota on the sampled blocks is being recorded photographically once a month, using a special underwater camera frame. Every three months, eight blocks, two of each type, are removed and brought to the laboratory. The biota on each block is observed, identified and quantified. Each side of every block is carefully photographed. These photographs are used later for computerized image analyses that will yield precise measurements of the species richness and biological diversity apparent on each block. Samples of the fouling biota are taken from the blocks and submitted for chemical testing for nine heavy metals. These analyses may indicate the occurrence of any leaching of heavy metals. The blocks are then sent to the National Building Laboratory for final mechanical strength tests.
The blocks have survived winter storms perfectly and four batches of eight blocks each have been retrieved so far for a detailed analysis. Positive findings at the end of the present study will encourage the establishment of fields of artificial reefs with fly ash as a major component on the Mediterranean continental shelf of Israel. Such fields will recruit commercially important marine species that will benefit the Israeli fisheries.