During the disaster relief phase the carbon footprint of disaster waste management is usually considered to be of lower priority than immediate restoration of infrastructure to provide food, potable water and sanitation. On the other hand, many activities that heavily impact on the carbon footprint of early recovery are irreversible, so the respective actions were considered and evaluated carefully. E.g. the dumping of coco waste materials on dumpsites is an irreversible process that increases the contribution to global warming.
The Situation after Super-Typhoon Yolanda
33 million coco trees had been felled by super-typhoon Yolanda in November 2013. Various working groups were trying to find solutions to cope with a huge number of coco trees. Most options included the production of coco lumber for reconstruction.
During the production of coco lumber coco saw dust, bark and leaves are generated as waste. Under normal, pre-Yolanda conditions this waste would not have constituted an environmental problem. But at the current amounts of coco lumber produced from the fallen trees, the coco waste was expected to become an environmental problem if not handled properly.
During many field visits, our team had noticed a large and growing number of burned coco tress, but also coco sawdust, lumber and whole tree trunks on community dumpsites. We evaluated various issues related to coco tree processing and waste management procedures.
According to Philippine legislation, “waste generated from planting or harvesting of crops, trimming or pruning of plants and wastes or run-off materials from farms or fields” is considered agricultural waste and to be treated as waste.
Dumping of coco tree waste
The dumping of coco sawdust and other coco waste increased the environmental impact of Yolanda, as organic materials in waste dumpsites are converted into methane by microbiological processes. Compared to carbon dioxide (CO2), methane (CH4) acts as a greenhouse gas 21 times as potent as CO2.
The following estimates demonstrate various options for handling of coco waste and related issues.
Assuming that only 10% (3.3 million) of the coco trees would be processed , and assuming that 0.25 t of coco waste would be generated per coco tree, about 825,000 metric tons of wood waste would be generated by coco tree processing.
Apart from the CO2 footprint, dumping of coco waste on dumpsites also consumes dumpsite space and reduces dumpsite life spans. At an average density of 0.55 t/m³ of coco waste, and a conversion factor of 1:1.4 for volume of solid materials to shredded materials, the volume of waste from 3.3 million processed coco trees would have been approximately 1,000,000 m³. This volume equals approximately four times the estimated disaster debris hauled to Santo Niño dumpsite during the first four months after Yolanda, or the production of municipal solid waste of the city of Tacloban of more than 16 years.
With a carbon fraction (C) of 50% in the coco waste (412,500 t), and a C to CO2 (carbon dioxide) ratio of 3.66, CO2 emissions of 1,500,000 t would be generated by burning all of the coco waste.
With a carbon fraction C of 50% in the coco waste and a 1.33 C to CH4 (methane, landfill gas) ratio, 550,000 t of methane will be generated. At a CO2/CH4 greenhouse gas potential ratio of 1:21, the global warming potential of the methane generated by dumping the coco waste on dumpsites and landfills would produce a CO2 equivalent (CO2eq) of 11,550,000 t. In this scenario the CO2 emissions generated by the transport to the dump sites are not even included.
When composting or mulching (shred&spread) is applied to coco waste, only 50% of the carbon will be converted into CO2, the rest will be sequestered in the soil. Hence, CO2 emissions by mulching and composting can be estimated at 750,000 t for 3.3 million trees. Concerning livelihoods projects, there appears to be no market for raw compost, as the soil in the Philippines is mostly fertile already.
The table above compares the CO2 footprints of coco waste treatment options, based on the estimations made.
When converting coco waste into fuel or electricity by fuel briquette/biogas production or thermal gasification, the carbon footprint may be zero or even be positive if fossil fuels are replaced.
Our research revealed that the production of charcoal from coco lumber did not appear to be a viable option as the charcoal would be of poor quality and burns too fast. There seemed to be little demand for coco lumber based charcoal in general.
According to the table above, even burning the coco waste in the fields would be preferable to dumping. The most reasonable solution under the given circumstances was mulching on site.
Understandably, during the disaster response phase carbon emissions are not amongst the top priorities, but they should be taken into account in the early recovery phase and during return to development.
Dumping sawdust and other wood waste should not be encouraged, because it has by far the largest CO2 footprint compared to burning, mulching or biofuel production.