The principle behind biogas power generation is as follows: Organic wastes (such as animal excreta, kitchen waste, and organic sludge) undergo decom­posi­tion under anaerobic conditions (the absence of oxygen) to produce biogas (largely composed of methane). The gas is then purified to remove corrosive gases like hydro­gen sulfide, and is used to fuel combustion engines that drive generators to produce electricity.

In 1991 there were efforts by government agencies in Taiwan to incentivize farmers to set up biogas generation systems, but at that time the technology was not sufficiently mature. The biogas was sent directly to the generator sets without desulfurization, causing corrosion of the equipment by hydro­gen sulfide. Because most of the equipment used was imported, main­tenance was very expensive, and the experiment ended in failure. Following this learning experience, how is Taiwan now approaching biogas power generation?

Li Chih-chieh (right), manager of the Agricultural Energy Technology Development Department at ITRI’s Central Region Campus, and Martin Lin (left), director of Longsheng Livestock Farm, have been working together to solve the wastewater treatment problems faced by traditional livestock farms.

Building a biogas industry

The main obstacle is not technology. “We have long been well versed in the technology for biogas power generation, but the business model used in Taiwan was not yet up to speed,” says Li Chih-chieh, manager of the Agricultural Energy Technology Development Department at the Central Region Campus of the Industrial Technology Research Institute (ITRI). In line with the government’s energy transition policies, in 2016 ITRI began guiding private-sector enterprises to expand biogas power generation.

However, Li observes that there had been little investment in biogas power projects in Taiwan and there were few equipment dealers. These factors drove up ­equipment installation costs and made maintenance more difficult. The solution to this chicken-and-egg problem was to build an industry around biogas power generation.

Fortunately, although at that time Taiwan had no businesses specializing in biogas power generation, there were a number of industries with potential to branch out into biogas. “For example, companies that built diesel generators could use the same generator head, but a different fuel [i.e., biogas], thereby developing another line of business. Boiler vendors that specialized in steam generation for the food industry could also use their combustion technology for biogas power generation,” says Li.

On his own initiative, Li began to play the role of facilitator and matchmaker, visiting private-sector firms to advocate for biogas power generation, until finally he got businesses in fields such as power generators, boilers, gas treatment, and wastewater treatment to expand their operations, so that step by step an industrial ecosystem took shape. Today there are about 40 ­domestic vendors in the field of biogas power generation, which Li jocularly calls “Team Taiwan.”

There are many points to watch in wastewater treatment, making it a major headache for many pig farmers.

First deal with wastewater treatment

Meanwhile, Li also visited livestock farms all across Taiwan. He explains that farms that raise over 5,000 head of stock are especially suitable for biogas power generation because they produce sufficient amounts of organic waste.

However, he notes that a prerequisite for biogas power generation is proper handling of wastewater. There are three steps to wastewater treatment at livestock farms: First, animal excreta must be separated into solid and liquid portions, after which the liquid is first passed through an anaerobic digester, and then undergoes aerobic treatment. Anaerobic digestion is the stage of the process that generates biogas. However, this water treatment process involves crucial technical issues such as the size of the anaerobic digester vessels, the retention time of the wastewater within them, and how to dispose of the large amounts of sludge that are produced, so that wastewater treatment is often seen as a big headache by livestock businesses. If waste­water is not properly handled, the stench that it produces will create a nuisance, and it may also create pollution which may cause environmental protection agencies to order the farm to suspend its operations. Before such issues are resolved, livestock farmers will have little interest in using their waste for biogas power generation. With this in mind, Li not only provides suggestions, but also personally rolls up his sleeves and works with farms to solve their problems.

What’s especially problematic is that Taiwan is a small and crowded island where land is expensive, but wastewater treatment facilities require considerable space. Taking farmers’ business needs into account, Li suggested that without reducing their herd size, pig farms could transform their traditional pig sheds into modern pig houses with raised slatted or wire-mesh floors, allowing separation between the pigs and their excreta, and thereby reducing the vast amounts of ­water needed to clean pig houses and wash excreta off the ­animals’ bodies.

The microbe-rich sludge generated by wastewater treatment on pig farms can be put to good use in treating industrial wastewater.

Cross-sector collaboration

In addition, the large amounts of sludge produced during the anaerobic treatment of wastewater have to be extracted by pumping, which uses a great deal of electricity, and disposal costs range from some NT$7,000 to NT$20,000 per metric ton. This represents a huge burden for pig farmers. Li searched for innovative ways to make use of this sludge, and realized that because it is rich in organic matter and microorganisms, it can be used in the treatment of industrial wastewater.

Li explains that industrial wastewater can be highly toxic, often containing strong acids or strong alkalis with little organic matter. But the farm sludge contains many different microorganisms, and when added to industrial wastewater it can degrade the toxins biologically, meaning that factories no longer need to add yet more chemicals to treat their wastewater. Thanks to Li’s efforts in locating potential users, this waste product that was formerly a headache for pig farmers has been transformed into a valuable asset, and many firms in the petro­chemical, textile, and optoelectronics sectors are even happy to collect the sludge from pig farms themselves.

As for smaller pig farms, they can still turn their biogas into thermal energy to keep piglets warm, thereby replacing energy-hungry heat lamps.

Li’s sincere actions finally persuaded many livestock farms to join the ranks of green energy suppliers. “Taiwan currently has 134 livestock farms with 5,000 or more head of stock, and some 70–80% of them are using biogas to generate electricity or produce thermal energy.” 

Properly treated wastewater does not smell foul, but has a delicate fragrance like green grass.

Circular systems on pig farms

On a hot August day, Li takes us to visit Longsheng Livestock Farm in Changhua County’s Fangyuan Township. Farm boss Martin Lin guides us through his extensive farm to the final sedimentation tank of the wastewater treatment system. Pulling out a tube, he shows us that the treated wastewater that is about to be discharged is a light grey-green color and gives off no unpleasant odor, but has a faint grassy fragrance. With broad smiles on their faces, Lin and Li both say, “To see that wastewater can be treated to this level is really heartwarming.”

Longsheng is a pig farm that Lin purchased only eight years ago. Unlike many pig farms, which cover their entire land area with pig sheds in pursuit of ­production efficiency, Longsheng had a good basic infra­structure for environmental protection. Seeing this, Lin believed the farm had excellent development potential, and was willing to pay a premium price for it. The farm has been operating for nearly half a century, and is further evolving under Lin’s leadership. Today it has 12,000 pigs, and besides using water-­saving pig houses with raised floors, Lin has installed biogas-fueled generators which power the farm’s ventilation fans. In addition, he has planted many trees around the pig houses to lower the ambient temperature, while rows of solar panels are installed on the roofs. He has also switched over to double-layered walls for insulation and uses extra-thick sheet-metal roofs to lower interior temperatures.

Pork plays an important role in Taiwan’s dietary culture, and many families once earned extra income by raising pigs as a sideline. As traditional industries evolve to keep pace with changing times, animal husbandry will no longer be just a provider of food, but also a generator of green energy, and will stand side by side with other industries in combating climate change. The transformation of Longsheng Livestock Farm is a modernization process that today’s animal husbandry industry will have to undergo.

These giant sausage-­shaped red plastic storage bags are filled with biogas.