A cesspool exploded in the central Chinese city of Zhangjiajie, causing a building to collapse and injuring 15 people, according to state news agency Xinhua.
The incident happened last November 23, as a man tried burning waste beside the cesspool that caused the methane from the pit to explode. Three of the injured had to be hospitalized. It’s unfortunate that in the Middle Kingdom’s rush to build its infrastructure, safety standards have often been compromised. What’s lamentable is the fact that the technology to safely harness the methane has been available in China for centuries, and it don’t even cost an arm and a leg to construct.
Germany has 8,700 biogas plants which it uses to run 3,400 MW of electric generation capacity, but China leads the world in biogas use. This is because in the provinces of Szechuan and Yunnan, there is a long standing tradition of building underground pit-type digesters. These tanks are around 10 cubic meters (2,600 gallons) in size and are constructed from brick and traditional Chinese concrete. The cost of these systems is just $85 a unit and they even are able to provide cooking gas for stoves. Some are even used to produce electricity when these residential digesters are connected to 60 cubic meter village scale plants. Unfortunately, the technology is unheard of in Hunan, as well as China’s other provinces.
In other temperate countries, biogas digesters need external heat to activate the bacteria that process the waste. The traditional septic tanks are located underground and are oversized and hence are able to generate enough heat to produce methane all year-round. One doesn’t even need to use up all the methane as it can be stored and used only when needed, unlike wind and solar energy.
Modern methods of producing biogas not only produce methane for cooking or electricity, they also produce high quality fertilizer that can be used in landscaping or gardening. It’s easier to make organic fertilizer in digesters than from compost pits since they are self-contained – eliminating hazards from pests and locking in smelly odors.
What’s more, they could even save life and limb, among other things. Hopefully the authorities in China and elsewhere are able to digest the implications of promoting residential biogas.