During interviews with the press and at a recent demonstration in Long An Province, the 59-year-old bubbled over with excitement about the ecological and financial benefits of the machine, which has already received orders from abroad.
For 25 years, Hoa and fellow scientists Luu Van Chau and Tran Phi Phung have worked off and on together on a variety of projects, from afforestation to resort construction.
In 1990, they thought of using hydrogen gas to provide a clean, valuable source of energy for fishing boats.
"I knew this could be useful since fishing boats use thousands of litres of oil on their trips," Hoa said.
The generator ran on hydrogen gas, but it was considered too expensive for many fishermen.
"That machine separated hydrogen from oxygen through electrolysis. But we used the precious metal platinum, which is expensive. Each water electrolysis session cost more than VND10 million (US$445)," he said.
Hoa then considered cellulose as an energy source, but the results were less than satisfactory, and it was costly as well.
After years of conducting research about hydrogen, the three scientists thought rubbish would be a viable energy source.
"I once owned a resort, where there was much garbage. Also, there was a lot of poultry that had died from bird flu, so I thought we could treat them as well," Hoa said.
Working at a rubbish dump in Lam Dong Province's Duc Trong District, Hoa was able to generate syngas (a combination of carbon monoxide, carbon dioxide and hydrogen) from rubbish.
The syngas, however, could operate a 10KW electricity generator for only 45 minutes, he said.
Hoa and his colleagues had to suspend the project, as they had run out of money and owed suppliers VND8 billion (US$355,900).
In 2013, Hoa and his fellow scientists Chau and Phung resumed their research on hydrogen gas and waste-treatment processes in Long An Province.
They used syngas to produce methanol, which was used to produce DME, dimethyl ether, a clean and colorless gas which discharges little waste.
The DME gas was successfully used to operate a 100KVA electric generator.
"DME gas has been used for a long time in the world, but we can generate it at a low expense thanks to our success in having a cheap hydrogen source from rubbish." Hoa said.
He said that developed countries often treat garbage by using steam from water, or heat from fire, to generate electricity.
His invention, however, needs only DME gas, and treats unsorted rubbish, without any waste discharge to the environment.
"Through rubbish, I've learned many things. I can get oil, diesel and DME from rubbish to use for electricity generation," he said.
"People think that rubbish is just something to throw away. When burned, it emits smoke, which is bad for health. Now, with this technology, it is not only safe but gives us electricity and biochar," Chau said.
"I don't see anyone in the world using DME gas to generate electricity at a high capacity," he added.
The machine that he and his colleagues (along with other scientists who have contributed to the research in recent years) does not require users to sort the garbage.
It chops up the rubbish and then turns it into DME gas. The machine can also treat rubbish that had been placed in dumping grounds, according to Hoa.
Hoa's company has already achieved success. Several companies in the Philippines have ordered 12 machines, with a daily capacity of 400 tonnes of rubbish each.
A company in the US has also ordered a machine with a capacity of 300 tonnes of rubbish, and a Cambodian partner has asked him to work together to treat rubbish.
"They suggested a charge of US$15 for well-off households and US$4 for poor households. Next month, I plan to meet them," Hoa said, adding that a Nigerian company had also asked him to cooperate in a project.
In Viet Nam, a number of companies in Thanh Hoa, Vinh Phuc, Thai Binh, Kien Giang, Long An have ordered the entire waste-treatment system.
A machine at the lowest capacity (100kg rubbish per hour) can generate 20kWh electricity, and a larger machine can treat 12 tonnes of rubbish per hour, according to Hoa.
Every day, HCM City discharges roughly 10,000 tonnes of garbage, and most of the rubbish is placed in dumping grounds. A small part of the city's garbage is burnt to generate electricity, but sorting of rubbish is required first.
Hoa said that, with his technology, the city could generate about 3,500MW of electricity from 10,000 tonnes of rubbish, depending on the moisture level of the content.