Making Biogas from Tofu Waste

KOMPAS/MEGANDIKA WICAKSONO

Caretaker of the Biolita Waste water Treatment Network IV Wardoyo demonstrates the process of tofu waste water treatment in Kalisari village, Cilongo district, Banyumas, Central Java, Saturday, May 6. There are five wastewater treatment facilities in the village, with input from 142 tofu makers, which produce biogas for 210 households. Instead of polluting the environment, the wastewater can now be used to cook.

White smoke billows from the kitchen at the house of 52-year old woman, Tumirah, a tofu maker in Kalisari village, Banyumas, Central Java.

Burning wood boils the soybean stew in a large stove called kawah, or crater, by the locals.

Wastewater from the process of turning soybeans into tofu is piped to a digester container, about 300 meters from Tumirah’s house. The wastewater will be processed into biogas.

The biogas is then channeled through a smaller pipe to Tumirah\'s house to light the stove for cooking her daily necessities.

"I sometimes fry some meatballs for lunch with the biogas stove. In addition to cooking side dishes, it can also be used to cook vegetables and boil water," Tumirah said.

While demonstrating how to operate her biogas stove, Tumirah said her family had been using biogas for cooking for three years. After opening the gas line connected to the stove, she turned on the switch and lit a match above the stove. Blue flame, with a steady blaze, immediately appeared. "The flames are good and I prefer using biogas than an LPG canister for fear of explosions," she added.

In addition to being safer, Tumirah also claimed biogas helped her be more frugal in terms of spending. For biogas, she only needs to drain wastewater from her tofu production and pay Rp 15,000 per month to the manager of Biolita IV (the biogas installer) for pipeline maintenance and biogas management. Biolita stands for Tofu Waste Biogas.

"If you buy three kg of LPG it costs Rp 20,000. With biogas, I can save," she added.

In a day, Tumirah processes 80 kg of soybeans to produce yellow tofu. From that amount, the wastewater from tofu stew can reach 30 buckets. As each bucket has a capacity of 20 liters, the total volume of the yellowish, foamy and smelly wastewater reaches as much as 600 liters a day.

"Wastewater used to be immediately discharged into sewers and rivers. Now it can be processed into biogas," she said.

Another tofu maker, Sugeng Riyadi, 35, said, every day he uses 60 kg of soybeans to make fried tofu. The liquid waste from processing the tofu reaches 12 buckets or 240 liters. "Now wastewater from tofu is piped into a biogas digester. It used to be dumped into the river and caused a lot of fish to die and produced a strong smell," Sugeng said.

Waste

According to the chief of the Kalisari village, Aziz Masruri, the village has been known as a tofu-producing center since the 1970s. The tofu from the village is chewy and solid, but not sour.

The village has been known as a tofu-producing center since the 1970s. The tofu from the village is chewy and solid, but not sour.

In the village, which has a population of 4,671 people, or 1,512 families, there are 250 tofu makers. On average each tofu maker processes 50 kg of soybean per day and can produce 1,500 pieces of tofu.

With the price of tofu at Rp 600 per piece, the turnover from the sales in the village can reach Rp 225 million per day. In the past, the wastewater caused serious pollution to the river with the water becoming dense, smelly and foamy. Fish could not live in the river. "It used to be a dirty river. In addition to being unsightly, the smell was so strong," Aziz added.

Aziz said the villagers require between nine and 10 tons of soybeans a day. The liquid waste can reach seven liters for every 1 kg of soybeans. In one day, about 70,000 liters of liquid waste was dumped into the river.

The pollution problem was resolved by the construction of five wastewater treatment plants (IPAL), which were built in phases between 2010 and 2014 with the help of a number of institutions including the Research and Technology Ministry, the Central Java Environment Agency, the government of Banyumas Regency, and the local community.

"Now, 142 of the village’s 250 tofu makers pipe their wastewater to the digester containers, which generate biogas for 210 houses," Aziz said. Currently, the wastewater treatment plants are managed by five groups from Biolita I to Biolita V.

Aziz acknowledges there is still weak coordination and management among group members so the maintenance and utilization of biogas of each group is not optimal. "For example, in Biolita III many pipes have been damaged and broken. The village has allocated Rp 8 million for repairs," he said.

The same view was shared by Taryo, 54, a tofu maker of Biolita I. Taryo, who has processed 75 kg of soybeans a day for the past two years, is no longer able to use biogas because the stove and pipes are damaged. "We do not use biogas for cooking. The sewer pipes to the digester container were blocked two months ago," he said. He hopes the problem can be resolved soon.

Since 2016, tofu production has begun to decline so that now wastewater for Biolita IV reaches only about 60 percent of its capacity.

Wardoyo, 42, the manager of the Biolita IV wastewater treatment plant, admitted that problems often occurred due to the large amounts of dirt, wood and leaves in the wastewater container. "Garbage must be removed because it can clog pipes and waste containers," he said.

He is pays Rp 150,000 every month to maintain the Biolita V wastewater treatment plant, which consists of two digester units each with a capacity of 16,000 liters per day. The facilities were built in 2014. The wastewater treatment plant receives liquid waste from 73 tofu makers and supplies biogas to 107 homes, 24 hours a day.

However, since 2016, tofu production has begun to decline so that now wastewater for Biolita IV reaches only about 60 percent of its capacity. "As the raw materials decline. We implement an open and close system. Gas is distributed to the residents\' houses from 6 am to 5 pm, "said Wardoyo.

Vegetable protein

Lecturer of food science and technology program at the Faculty of Agriculture, of University of General Soedirman (Unsoed), Purwokerto, Rifda Naufalin, said tofu liquid waste contains vegetable protein, vinegar and organic acid and has a slightly acidic pH content.

"If the organic material is fermented, it can produce methane gas that can be used for cooking," she said. Rifda, who also serves as the head of Unsoed Food, Nutrition and Health Research, said untreated liquid wastewater had a pH of 4-5, which can kill fish and cause rice crop failure. The organic materials, if not managed properly, will decay and produce ammonia gas that produces a bad smell.

Rifda said biogas processed from the wastewater of tofu production is safe for residents to use because it has no pressure like the commonly used Liquid Petroleum Gas (LPG).

According to Rifda, the sustainability of biogas production must be maintained by training and improving the skills of residents to manage wastewater treatment plants.