Energy from the Landfill

Since it was officially launched in 2023, the Putri Cempo Waste to Energy Power Plant (PLTSa) in Surakarta, Central Java, has not been operating at full capacity. This is despite the fact that PLTSa Putri Cempo had once been widely touted as a solution to the growing waste problem in the city of Surakarta.

This prestigious project in the "City of Bengawan" faces two main issues: the project's economic viability and its technical readiness. Beyond that, a review by Commission XII of the House of Representatives (DPR RI) in mid November last year identified another problem, a miscalculation in the amount of waste needed to run the plant.

PLTSa Putri Cempo uses a gasification mechanism to process waste into an energy source. The requirement is that dry solid waste be used, in order to increase the calorific value and the amount of gas produced through the waste gasification process.

The Ministry of Energy and Mineral Resources claims gasification allows PLTSa Putri Cempo to produce more electricity, since the process offers high energy recovery and efficiency. So, is this claim about gasification actually accurate?

Afif Faishal, S.T., M.T., a Mechanical Engineering lecturer at Universitas Muhammadiyah Surakarta (UMS), explained that the type of waste fuel used has a major effect on the gasification process. One key requirement is reducing the moisture content in the waste.

"Ideally, in the gasification process, waste needs to be dried first, down to a moisture level below 20 percent," Afif said when contacted on Tuesday (22/9/2026).

Afif has previously researched the gasification process as one way to address urban waste problems. In his research, Afif modeled a gasification simulation using municipal waste typical of Surakarta. The gasification process converts waste into synthetic gas, or syngas, rich in hydrogen, which can be used as fuel for the power plant. Hydrogen is one of the gases with the highest energy efficiency and is well suited as a source of electrical energy.

"The waste is converted into synthetic gas containing hydrogen, carbon monoxide, and methane gas. These gases can be burned, so converting waste into energy this way can add real value," he continued.

The sample Afif used was solid waste collected at the Putri Cempo landfill. The solid waste samples taken had already been sorted to remove hazardous waste, such as ceramics, glass, wire, and hazardous metals. He ran gasification simulations using Aspen Plus software to test the gasification parameters.

The two parameters tested in this research were the steam to waste ratio and reactor temperature. Water vapor functions as the gasification agent and affects the increase in hydrogen gas produced, while reactor temperature affects the thermochemical reaction driving syngas production.

Afif found that heating at a temperature of 700 degrees Celsius with a steam ratio of 3 could significantly increase hydrogen content. That heating process produced a syngas composition consisting of 64.33 percent hydrogen, 9.2 percent carbon monoxide, 26.62 percent carbon dioxide, and 0.04 percent methane gas.

Although testing was carried out at 700 degrees Celsius, Afif noted that the optimal maximum temperature limit for a gasification reactor is predicted to reach as high as 853 degrees Celsius, with a steam to feedstock ratio of 3.5.

"There's genuine potential, theoretically speaking, for Surakarta's municipal waste to be converted into syngas with a high hydrogen content," he explained.

Afif's research, titled "Optimizing Operational Parameters To Maximize Hydrogen Enriched Syngas Yield From Municipal Solid Waste Gasification: A Strategic Waste to Energy Framework For Urban Sustainability In Surakarta," was published in the Journal of Applied Science and Engineering in late 2025. 

This gasification modeling study currently sits at Technology Readiness Level (TKT) 2 to 3. The simulation serves as the basis for developing a gasification reactor prototype that could later be used to directly process municipal waste in the Surakarta area.

Turning waste into fuel for a power plant does require significant extra effort and financial support. Even so, this step needs to be taken to address the growing pile up of urban waste.

Afif isn't stopping his research here either. He plans to develop a micro scale gasification reactor that could be used to manage waste at the neighborhood and sub district level. This follow up research is also the topic of his doctoral dissertation, as he's currently pursuing a doctorate at Universitas Sebelas Maret.

"The reactor we're designing going forward is meant to be lab scale, or micro scale. Later on, we can apply it to direct experimental testing using actual waste samples from Surakarta," he explained.

This prototype, he said, is expected to help address Surakarta's waste problem more efficiently. The target is to reduce the rate at which residents of Surakarta produce waste.

"The design will be simpler and more economical going forward, to help cut down on operational costs," he added.

Dozens of waste trucks of the Surakarta City Government move in and out of the Putri Cempo landfill (TPA) constantly. This open dumping site, built back in the 1980s, receives up to 400 tons of waste per day. The waste to energy power plant (PLTSa) was later built on the Putri Cempo site in 2023.

The central government first initiated waste to energy power plants, or PLTSa, back in the 2010s. The government planned 12 PLTSa facilities as pilot projects spread across several regions in Indonesia, including Putri Cempo.

Along the way, PLTSa Putri Cempo turned out not to be running optimally and stalled partway through. On 15 November 2025, Commission XII of the House of Representatives (DPR RI) raised concerns about PLTSa Putri Cempo. Deputy Chair of Commission XII, Sugeng Suparwoto, identified two problems holding back the plant's operations: the project's economic viability and its technical readiness.

Commission XII's report also found that the initial feasibility study had failed to accurately predict Surakarta's waste output. PLTSa Putri Cempo needs 500 tons of waste derived fuel per day, fuel obtained from high calorie solid waste.

However, Surakarta's waste production hasn't been able to meet that fuel requirement. Instead of getting waste that matches what the plant actually needs, more than 60 percent of the waste at TPA Putri Cempo turns out to be organic waste. This household waste hasn't even been sorted. "The raw material doesn't match what the machine needs," Sugeng said.

Writer: Gede Arga Adrian

Translator: Farizal Luqman Majid

Editor: Al Habiib Josy Asheva

Designer: Muhammad Nur Haqqi