The Ecosystems Research and Development Bureau (ERDB) has replanted 42 hectares of mined-out Bagacay Mine in Western Samar, which has regenerated heavily metal-laden soil through “bioremediation”.
Species used that have aesthetically greened the area are Mount Agoho (Gymnostoma rumphianum); vetiver (Vetiveria zizanioides); narra (Pterocarpus indicus); Acacia auriculiformis; and mangium (Acacia mangium).
“Today the aesthetic condition of the waste-dump area has improved. A total of 42 hectares of mined-out area have been successfully planted already. The project has also provided employment to the surrounding community,” ERDB Director Henry A. Adornado said in a statement.
The joint project of ERDB and the Mines and Geosciences Bureau (MGB) called An Integrated Science-Based Approach in the Rehabilitation of Mined-out and Waste Dump Areas in Bagacay, Hinabangan, Samar, started in 2009 in the mined-out area of Bagacay—a 2,672-hectare former copper and pyrite area.
Bagacay Mine used to be operated by Marinduque Mine Industrial Corp. from 1956 to 1985 and by the Philippine Pyrite Corp. from 1986 to 1992. It ranked first in the general risk ranking among the seven inactive mines in the Philippines.
In the joint research by the ERDB and the MGB, both attached agencies of the Department of Environment and Natural Resources (DENR), three experimental blocks of land measuring 20 meters by 50 meters have been put up. All these three experimental blocks were chosen for having been laced with heavy metals.
“The ERDB determined the potential of selected indigenous tree species in regreening and absorbing toxic elements in the abandoned mined-out area,” said Adreana Santos-Remo, ERDB information officer.
After the study period, high concentrations of heavy metals were recorded for Mount Agoho, mangium, A. auri and narra. This showed that the four species planted on the metal-filled soil were most efficient in absorbing the metals and in distributing heavy metals from their roots to leaves.
“All hope is not lost for the environment. The initial results of the phytoremediation study conducted by the Department of Environment and Natural Resources-ERDB and the MGB revealed that mined-out areas can be rehabilitated through the use of appropriate technology,” Adornado said.
ERDB forester Gregorio E. Santos Jr., study project leader, said that with the inherent bioremediation (metal and pollutant absorption) capacity of selected tree species, along with the fertilization technique, an observable increase in the height of mangium and Agoho del Monte was observed in the former mine.
Biomass (dried leaves and branches) produced by narra was noted to provide nutrients to the soil, which prompted the growth of grasses and other shrub species.
The research also revealed that organic fertilizer treatment could work well in areas like the Bagacay mine.
The combination of 1-by 3-meter forest soil, 1-liter agricultural lime and 3 liters of organic fertilizer (chicken manure) was found to be the best treatment for the four tree species that were included in the study, according to the ERDB.
The ERDB said it hopes that the joint research would inspire other mining companies to use similar rehabilitation protocols to bring back the natural state of the mined-out areas in the Philippines.
The agency is also implementing the use of other ERDB-developed technologies, such as carbonized biomass and Hi Q Vam 1 in this endeavor. The ERDB experts applied Hi Q Vam on the plants while they were growing.
Hi Q Vam, also mycorrhiza, is a fungus that has a symbiotic relationship with plants. Mycorrhiza resides in plant roots and causes soil nutrients to retain in the roots, causing survival and growth in plants despite adverse soil condition, such as heavy-metal content.
Adornado said Section 47 of Presidential Decree 705 of the Revised Forestry Code of the Philippines requires mining companies to restore mined-out areas as near to its former natural state before the mining operation.