Biochemistry lessons from landfills

In a recent disclosure to the Philippine Stock Exchange, listed firm Basic Energy Corp. said it is planning to enter into a memorandum of agreement with two local firms, namely New Kanlaon Construction Inc., and Integrated Environmentwaste Processors Corp., and two South Korean firms ReTech Solution Co., Ltd. and Eco-Frontier Co., to conduct a feasibility study for a landfill gas to power project in San Mateo.

The project would harness methane from a closed dumpsite to generate electricity with revenues coming from power sales and carbon credits.

Earlier, in July, Montalban Methane Power Corp. in cooperation with Carbon Capital Markets, a UK-based financier and carbon credits trader, is developing an initial 2 MW power plant using methane coming from the Rodriguez, Rizal landfill at a cost of some P 1.5 billion.

A few years back, I remember some company was looking for methane at the Payatas dump site, but apparently nothing came out of that project.

How could a despicable place where all sorts of waste are thrown in generate enough methane to produce electricity?

Elementary, my dear Watson; it is bacterial decomposition.

The whole process is a wonderful symphony of cooperative bacterial processes which, for tracking purposes can be broken down into four phases.

Phase 1 begins with aerobic (oxygen-loving) bacteria breaking down long molecular chains of complex carbohydrates, proteins and lipids in waste into simpler compounds. In the process, carbon dioxide is produced while oxygen is depleted.

In Phase 2, anaerobic bacteria begins to proliferate in the absence of oxygen and converts the compounds created by the aerobic bacteria into acetic, lactic and formic acids, as well as alcohols like methanol and ethanol. This makes the environment acidic. Under these conditions, certain nutrients are dissolved liberating nitrogen and phosphorous, which are key growth factors of another kind of bacteria which produce carbon dioxide and hydrogen as byproducts of respiration.

Now, if the landfill is disturbed at this stage, the environment becomes oxygenated again and one goes back to Phase 1. This is probably happening at Payatas, where hordes of scavengers continuously disturb the landfill.

No wonder no sufficient methane was found.

We have a little lesson here: human scavenging does not promote decomposition.

In Phase 3, the remaining organic acids are consumed, forming lactates which cause the landfill to become neutral. This promotes the formation of colonies of methane-forming bacteria. The methane- and acid-producing bacteria become symbiotic, delicately waltzing together to the music of a biochemical orchestra. The symbiosis is so well coordinated that the amounts of methane and carbon dioxide produced are near 50-50 in most landfills. The rest of the gases comprising of hydrogen sulfide, nitrogen and hydrogen mostly, does not normally exceed 2 %.

Phase 4 occurs when both the composition and production rates of the gases remain relatively constant. This constancy is used to determine whether a landfill is ripe for picking for methane.

The methane gas can be produced at a stable rate for about 20 years; but can sometimes last up to 50 years after waste has been initially placed. This is the best time to put up that gas-to-power project.

It is an inspiring microbiological and biochemical symbiosis. Years ago, all I thought biochemistry was an unending parade of DNA base pairs. amino acid sequences, and metabolic pathways too complicated to trace, but nevertheless, required to be understood partially to pass the course.