Success Stories: Lead Paste Desulfurization Units in Indonesian Recycling Plants

In the heart of East Java, where the hum of industry mingles with the scent of jasmine from nearby villages, lies PT. EcoRecycle Indonesia—a mid-sized recycling facility that has become a beacon of sustainable waste management in the region. Five years ago, however, the story was very different. "We were drowning in compliance issues," recalls Pak Agus, the plant's operations manager, as he gestures toward a row of gleaming silver machinery. "Our lead acid battery recycling line was spewing sulfur emissions, our wastewater tests kept failing, and the local government was threatening to shut us down. Today, we're not just compliant—we're setting standards. And it all started with upgrading our lead paste desulfurization unit."

Lead acid batteries are ubiquitous in Indonesia—powering everything from motorcycles to backup generators. With millions reaching end-of-life each year, recycling them is critical to recovering valuable lead and reducing environmental harm. But the process is fraught with challenges, especially when it comes to handling lead paste, a toxic byproduct rich in sulfur compounds. For PT. EcoRecycle, like many Indonesian recyclers, this step was once the weakest link in their operations. Let's dive into how a targeted investment in lead paste desulfurization technology transformed their fortunes—and what other plants can learn from their journey.

The Pre-Desulfurization Nightmare: A Plant on the Brink

Before 2019, PT. EcoRecycle relied on a basic lead acid battery recycling setup: manual battery breaking, crude lead separation, and open-air smelting. "We thought we were doing the right thing by recycling, but we were blind to the damage," says Pak Agus. The real problem? Lead paste, which makes up about 40% of a battery's weight. When heated in their old smelting furnace, the sulfur in the paste reacted with oxygen to form sulfur dioxide (SO₂)—a pungent gas that irritates the lungs and contributes to acid rain. "Our workers wore masks, but you could still smell it. Villagers complained of coughing fits, and the air quality monitors at the plant gate never stopped beeping," he adds.

Wastewater was another disaster. The paste, when mixed with water during separation, leached heavy metals like lead and cadmium, along with sulfates. "Our effluent treatment machine equipment was a relic from the 90s—a basic sedimentation tank that barely reduced lead levels to 2 mg/L, well above the government's 0.5 mg/L limit," explains Siti, the plant's environmental officer. "The local river ran murky near our discharge point, and fishermen stopped casting nets there. We were stuck in a cycle: pay fines, patch up old equipment, repeat."

Financially, the inefficiencies stung too. Without desulfurization, much of the lead in the paste was lost as slag, reducing recovery rates to 75%. "We were throwing away money—literally," Pak Agus sighs. "And with global lead prices fluctuating, those losses ate into our profits. We knew we needed a change, but with limited capital, where do you even start?"

Discovering the Solution: Lead Paste Desulfurization Units

The turning point came in early 2019, when Pak Agus attended a recycling technology expo in Jakarta. There, he encountered a vendor showcasing a lead paste desulfurization unit—a compact system designed to remove sulfur from lead paste before smelting. "I was skeptical at first," he admits. "But when they showed me the data—how it could cut sulfur emissions by 90% and boost lead recovery to 95%—I was hooked. The question wasn't 'Can we afford this?' It was 'Can we afford not to?'"

Lead paste desulfurization works by chemically converting soluble sulfate compounds in the paste into insoluble ones. At PT. EcoRecycle, the chosen unit uses a sodium carbonate solution to react with lead sulfate, forming lead carbonate (a stable, low-sulfur solid) and sodium sulfate (a soluble salt). "It's like neutralizing a acid with a base—simple chemistry, but the engineering makes it efficient," says Andi, the plant's head engineer, as he points to a series of stainless-steel reactors. "The paste is mixed with the solution in a stirred tank, then sent through a filter press equipment to separate the solid lead carbonate from the liquid sodium sulfate. No more sulfur in the smelter, no more heavy metals in the water—at least, not in the same quantities."

But desulfurization alone wasn't enough. To fully solve their problems, PT. EcoRecycle needed to integrate the new unit with other systems: a modern filter press to handle the solid-liquid separation, an upgraded effluent treatment machine to process the sodium sulfate-rich filtrate, and an air pollution control system to capture any remaining emissions. "It was a package deal," Pak Agus says. "We couldn't just plug in a desulfurization unit and call it a day. We needed a holistic approach."

Integration in Action: From Lab to Line

Installing the new equipment took six months—longer than expected, but worth every delay. "The biggest challenge was training our team," Andi recalls. "Our workers were used to manual labor; suddenly, they were operating touchscreen controls and monitoring pH levels. We brought in trainers from the equipment supplier, and even sent two technicians to China for hands-on training. It was tough, but now they're the most knowledgeable crew in the province."

Let's walk through the revamped process step by step, starting from battery intake to final lead ingot:

1. Battery Breaking and Separation: Old batteries are fed into a mechanical cutter, which splits them open. Plastic casings are shredded for recycling, while lead grids and paste fall into a separator. "We upgraded to a high-speed cutter that reduces break time by 30%," Andi notes.
2. Lead Paste Collection: The paste is sluiced into a holding tank, where it's mixed with water to form a slurry. "This used to be a messy, manual step—now it's fully automated," he adds.
3. Desulfurization: The slurry is pumped into the desulfurization reactor, where sodium carbonate is added. Sensors monitor pH in real time, ensuring the reaction is complete. "We hit a 98% desulfurization rate consistently now," Andi says proudly.
4. Filter Press: The reacted slurry enters a filter press equipment, which uses hydraulic pressure to squeeze out liquid. The result? A dry cake of lead carbonate (ready for smelting) and a filtrate rich in sodium sulfate.
5. Effluent Treatment: The filtrate is routed to the upgraded effluent treatment machine equipment, which uses chemical precipitation and membrane filtration to remove sodium sulfate and any remaining heavy metals. "Our discharge now has lead levels below 0.1 mg/L—better than the national standard," Siti grins.
6. Smelting with Air Pollution Control: The lead carbonate cake is fed into a modern smelting furnace. "With almost no sulfur left, SO₂ emissions are down to 50 mg/Nm³—way below the 350 mg/Nm³ limit," Andi explains. Any residual emissions are scrubbed by the air pollution control system equipment, which uses activated carbon filters and a wet scrubber.
7. Lead Refining: The molten lead is purified in a refinery kettle, removing impurities like antimony and tin. The final product? 99.99% pure lead ingots, sold to battery manufacturers at a premium.

"The difference is night and day," Pak Agus says, gesturing to a wall of certificates. "We've passed every government inspection since 2020, and our ISO 14001 certification hangs right there. But the best part? The community no longer sees us as a threat. Last month, the village head even asked us to give a talk at their environmental awareness day."

By the Numbers: The Impact of Desulfurization

To quantify the change, let's compare key metrics from 2018 (pre-upgrade) and 2023 (post-upgrade) at PT. EcoRecycle:

"The numbers speak for themselves," Pak Agus says. "We expected to recoup the investment in 5 years; we did it in 3. Higher lead recovery means more revenue, lower fines and operational costs mean bigger profits, and healthier workers mean less downtime. It's a win-win-win."

Beyond Compliance: A Model for Sustainable Recycling

PT. EcoRecycle's success hasn't gone unnoticed. Last year, the Ministry of Environment and Forestry featured their plant in a national case study, and three other recyclers in Java have reached out for advice. "We're not just a business—we're pioneers," Pak Agus says. "Indonesia's recycling industry is growing, but it needs to grow responsibly. You can't cut corners on environmental protection, especially with toxic materials like lead."

One key lesson? Don't underestimate the importance of auxiliary equipment. "A desulfurization unit is great, but if your filter press can't handle the slurry, or your effluent treatment machine can't process the filtrate, it's useless," Andi emphasizes. "We invested in high-quality filter press equipment and upgraded our effluent treatment machine equipment at the same time, and that's why we succeeded."

Another takeaway is community engagement. "We used to keep the plant closed off—now we host monthly tours for villagers and students," Siti says. "When people see the air pollution control system equipment humming and the clear water flowing out of our effluent plant, they trust us. That trust is priceless."

Looking Ahead: Expanding Horizons with Lithium and Beyond

With their lead acid battery line running smoothly, PT. EcoRecycle is now eyeing the future: lithium-ion battery recycling. "EVs are coming to Indonesia, and we need to be ready," Pak Agus says. "We're already researching li-ion battery breaking and separating equipment, but we'll apply the same principles—invest in clean technology, integrate with air and water treatment, and put the community first."

As we wrap up the tour, Pak Agus pauses by a wall of photos: the plant in 2018 (smoke billowing, workers in ragged masks) vs. today (greenery around the perimeter, workers in crisp uniforms). "This isn't just about machines," he says softly. "It's about proving that recycling can be both profitable and responsible. If a small plant in East Java can do it, anyone can."

For Indonesian recyclers grappling with lead acid battery waste, the message is clear: upgrading to a modern lead paste desulfurization unit isn't just a compliance measure—it's a strategic investment in sustainability, profitability, and community trust. As Pak Agus puts it: "The past smelled like sulfur. The future? It smells like opportunity."