Greening of Saline and Alkaline Sediments

Tata Chemicals Limited (TCL), which was established in 1939, today is the second largest producer of soda ash in the world with manufacturing facilities across four continents. TCL’s journey as a synthetic soda ash manufacturer began in Mithapur, on the coast of Gujarat, on India’s west coast, and for many years Mithapur represented the sum total of TCL’s soda ash manufacturing. Over time TCL’s Mithapur production volume has grown from 80 tons per day in 1944 to its current level of 2,400 tons per day. The volumes of wastes generated from its operations have grown as well. Solid waste disposal was one of TCL’s biggest concerns. Before setting up the cement manufacturing plant that converts these effluent solids into cement in 1993, all the solid waste generated was stored in a corner of the factory site called Malara.

Loss of land, dust emissions, poor aesthetics, public discontent, and regulatory pressures were the triggers for finding sustainable solutions. In course of time, people inhabited areas close to the site and the dump site became a point of discontent with the new residents due to dust constantly flying about, as high wind speeds prevail in these areas. To avoid the menace of dust, many attempts were made to reclaim the dumpsite through plantations, but the attempts were in vain.

A team was formed to work on alternative ways to improve things. The team came up with an innovative solution: The use of bio-fertilizers and bio-remediation techniques to remediate the solid wastes and develop a green cover. It has resulted in the effective utilization of the waste generated to grow the plantations and, hence, contributed to the improvement of the environment. Simultaneously, TCL developed techniques for filtration of effluent solids and its subsequent use for cement manufacturing in solids generation.

Nature is the best teacher – this was true for this project as well. Team members observed certain types of plants / grasses surviving in saline and alkaline lands in pockets of Mithapur, but their distribution was quite sparse. When their roots were studied in microbiology labs with the help of the TERI team (The Energy and Resources Institute, New Delhi), it was observed that a special group of microorganisms established themselves on the root system, thereby helping the plants / grasses to extract soil nutrients to survive and defend themselves against the natural adversaries it faced in that area. The TCL team engaged the services of TERI’s Centre for Mycorrhizal Research, Biotechnology and Management of Bioresources Division for the identification and isolation of observed special microorganisms, and to make pure culture samples of them in their laboratory. TERI was also engaged in establishing and maintaining the green belt.

The compatible bacterial and mycorrhizal consortiums were brought in and the plants’ (saplings) root systems were inoculated. Sediments were also treated and with that the plantation was completed. It was a success. The plants resisted the harsh sediments. The microorganisms helped the plants to extract the insulated nutrients that were not available and the plants survived and have since grown. Today, the dry and lifeless dumpsite has been transformed into a lush green plantation with about six varieties of plants and three varieties of grasses. About 22,000 plants and an equal number of grasses are growing with few support systems. A whole chain of biodiversity has started its life. Once upon a time, no species could survive and now plants, ants, frogs, snakes, insects, butterflies, and a variety of birds flourish in that area. Once upon a time, the sediments were considered as a waste and a nuisance and now they have turned into a substratum upon which one can cultivate cash crops like vegetables during favorable seasons with some management support. Growing plantations on inorganic chemical sediment without using soil and using saline water for irrigation was a dream come true for horticulturists.

All over the world in landlocked soda ash industries, the solids settle in the sediment basins (settling ponds) and after these reach a certain height, they shift to the next set of ponds. The settling ponds remain as mounds of solid wastes. Those soda ash industries that are on the seacoast discharge the effluents into the nearby sea. These unsustainable practices have led to plant closures in many countries. All over the world, 12 soda ash manufacturing sites have been closed due to environmental issues. No new plants have been built in the last 12 to 15 years in the developed world for the same reason.

The current innovation provides an opportunity to all those industries that have piled up large quantities of solid wastes to recover the dumpsite areas. Lifeless substrata can be converted into lush green belts.

Due to overexploitation of groundwaters, saline waters are moving into inland areas. Monsoons, loss of traditional groundwater replenishment basins due to urbanization, and change in rainfall patterns (rain intensity) have resulted in rainwater runoff instead of replenishment. Moreover, the lack of groundwater management is leading to severe groundwater depletions. Transfer of saline water into the coastal areas is a serious problem. Farmers that depend largely on groundwater for their farming are losing productivity year on year due to soil chemistry change (increasing salinity). However, the current technology will pave the way for restoring those degraded lands and restoring productivity.

Many industries (distilleries, thermal power plants, etc.) that end up with large volumes of non-hazardous solid waste mounds can now process their wastes much more efficiently and create lush green belts or even cash crops, depending on their geo-climatic conditions using this unique mycorrhizal-based technology.

Climate change can be addressed by converting the coastal deserts into green belts. Plants that can survive in harsh conditions (dust storms, sand storms, and saline water irrigation) can be chosen and cultivated. They can become large sinks for carbon dioxide over a period of time.

Areas that had lifeless substrata can now be converted into green fields rich in biodiversity. A variety of flora and fauna should be chosen, which is very necessary in depleted biodiversity conditions.

Today, of the 30 acres of the dumpsite area, 22 acres have been converted into lush green belts, and the area that was recently a barren wasteland is now rejuvenated and yields vegetables in favorable seasons.

No horticulturist could ever believe that a plantation could be grown without using any natural soil and by using saline water for irrigation on alkaline and saline sediments. (Table 1 – Zero time sediment analysis report). The substratum is an inorganic chemical sludge (nutritionally sterile) and after reclamation, it was converted into normal soil. Today, we observe secondary growth at the plantation (seeds fall, germinate, and grow), which was once an impossible task.

All over the world, the synthetic soda ash manufacturing industry had adopted the Solvay – Ammonia process, which was developed 150 years ago. About 250–350 kg of solid wastes are generated per ton of soda ash manufactured, and conventionally either they are discharged into the nearby water body (river / sea) or they are stored in stockpiles 7 to 40 meters high. Nowhere in the world was anyone able to convert the solid wastes into something useful.

The current project challenged the fundamental principles of biological science and made a near impossible thing a reality. No successful case studies were known whereby plants could survive and grow on such highly alkaline and saline sediments. This will help other similar industries to innovatively manage their solid waste problems. This will also pave the way to reclaiming saline-affected soil productivity in countries along coastlines.

Tata Chemicals approached the problem of a reclamation of stored solids in a 30-acre area and started with a pilot project of 2.5 acres. Since the previous attempts were not successful, technological intervention was required. The TERI team offered technological assistance to the TCL team. Both teams approached the problem and jointly worked together for nearly eight years with full enthusiasm and toward a common goal. Now it serves as a solution for many such industries. With its broad expertise and experience in providing sustainable technological solutions to the environmental problems faced by industries across the globe, TERI was a great support to TCL. Tata Chemicals was convinced that while addressing the local issue, the solution had wider national and international applications.

Since this project was the first of its kind, certain guidelines were set by the team itself, which really made the project unique.

The team decided not to use

• normal soil for plantation
• chemical fertilizers
• fresh water (scarce availability)
• any external species (biodiversity issues)

The team also decided that they should depend on and use

• plant / grasses that are halophytic (saline resistant)
• not palatable to cattle
• domestic solid waste as manure (treated STP sludge)
• suitable microorganisms for sustainable plant growth (to learn from nature)
• encourage more biodiversity through careful plant selection

The challenge of growing plantation on a lifeless substratum without using soil and fertilizers was a daunting task. Coordination between the TCL team and the TERI team was very important so that trust could be established and that they could work toward a common objective. Progress on the project was shared in a monthly review meeting, wherein any problems were solved in a short time. Apprehensions about the success of the project were projected even after five to six years of project implementation. But the team kept the hope that it would happen.

Withstanding all the hurdles and pressures, the TCL and TERI teams proved their mettle, and the proof of this can be seen today with the successful of the green belt cover over several sites in Mithapur and Padli near the TCL factory. These green belts testify to the years of cooperation and research that both teams have given to the project to make the area a better place to live. This project has set a benchmark for industries across the world to improve their triple bottom lines and thus move toward the global of sustainable development.