(In reaction to The Manila Times’ story “DENR orders review of waste facilities,” published on Jan. 27, 2026)
SPENDING on solid waste management is one of the largest any local government unit would do, after education and policing. As such, solid waste management — both as a science and an art — has matured using advanced mathematical techniques and various disciplines of natural and social sciences. Solid waste management in most countries is offered as a postgraduate course in environmental engineering. As a management system strongly influenced by local habits, tradition and culture, the application of scientific principles has to be adapted to local conditions.
The siting of landfills is critical in protecting the environment, especially in the Philippines, where limestone or “anapog” is prevalent. When the organic component of solid wastes decompose, acetic acid or vinegar is formed. Acetic acid is highly corrosive to limestone. Acetic acid is converted by anaerobic bacteria into methane and carbon dioxide. Carbon dioxide is almost 50 percent heavier than air and in the interspaces of decomposing solid wastes. It is not unusual for the carbon dioxide to reach 40 to 60 percent in volume, or 10,000 to 15,000 higher than that in the atmosphere. Carbon dioxide forms carbonic acid, which is also highly corrosive to limestone. A Google map search of several landfills in Cebu shows those are built in anapog areas. There is a need to closely examine and evaluate the stability of those areas.
If there is no other option, landfills operated in limestone or anapog areas must meet the highest standards to prevent puncture, leachate collection, and treatment.
I understand the Department of Environment and Natural Resources is reviewing landfill sites throughout the Philippines. I hope they will consider the abovementioned facts.
E.A.R. Ouano
The author is a retired environmental engineer and co-author of the Unesco postgraduate textbook “Management of Solid Wastes.”