For decades, gasification has held promise as a potential pathway to cleaner, more efficient energy from waste. The stumbling block? Gasification of mixed waste or biomass produces “tars” that render traditional gas-cleaning technologies ineffective. Tars range from heavy (think asphalt, dioxins) to light (similar to gasoline, diesel, kerosine).
Most available gasification technologies merely combust the gas immediately after gasification, a “staged incineration” process that offers little of gasification’s true potential to produce cleaner, more efficient energy from waste.
By contrast, Synova uses the proprietary OLGA® syngas cleaning process, from technology affiliate Royal Dahlman, to remove tars and other impurities.
After mixed waste has been sorted to remove recyclables, metals, glass, and earth, the residual waste is dried and sized to produce feedstock. This feedstock is then “gasified”, converted from a solid into a gas. This impure gas is then sent through the OLGA® system to remove tars and other impurities. The result is clean syngas, free of the unwanted compounds that result from conventional gasification and incineration.
Conventional gasification doesn’t include purification, producing gas that’s suitable only for burning. This limits its attractiveness relative to fossil fuels. Clean syngas, by comparison, can be used in processes that generate 2.0x to 1.5x more power per tonne of mixed waste than incineration or conventional gasification (staged incineration). It’s also a suitable substitute for natural gas in industrial processes and for specialty chemical production.
The result of more efficiency? Projects that can sustain themselves financially via competitive energy sales, rather than relying almost exclusively on high tipping fees.
Waste is Pure, If You Remove the Impurities
Energy from Waste—Without Incineration
First-generation waste-to-energy plants—so-called “mass burn” incinerators—generate electricity from garbage, burning unsorted mixed waste to fire boilers, which produce steam that drives steam turbine generators.
Second-generation plants are generally staged incinerators, producing a dirty syngas that is combusted immediately after gasification, often in the same vessel. Impurities in the syngas aren’t removed before combustion. Like heat from incinerators, heat from this process has but one use: to make steam for a steam turbine generator or process heating system.
By contrast, Synova’s process cleans the syngas, so it can produce power with a clean emission profile. Compared with first- or second-generation incinerators, the use of this syngas in combined cycle gas turbines displaces 2.0x to 1.5x the fossil fuels displaced by conventional waste conversion technologies. Said another way, it produces 2.0x to 1.5x the power output, which means 2.0x to 1.5x the revenue from power sales, reducing its reliance on tipping fees that are essentially impractical in the developing world.
Syngas—synthesis gas—is so called because it contains the constituents from which all organic matter can be synthesized: hydrogen, carbon, and oxygen.
When biomass or mixed waste is gasified, some of the material does not break down into its constituent parts, leaving long-chain hydrocarbons known as tars. Tars resulting from gasification can be composed of dozens of compounds, and include heavy tars (think of asphalt, dioxins) and light tars (think of gasoline, diesel, kerosene). These tars contain roughly 15% of the latent energy, but they also foul traditional means of removing other contaminants.
The OLGA process, which distinguishes Synova from conventional gasification or waste conversion technologies, removes heavy and light tars and segregates them for further processing to capture their latent energy value. With the tars removed, removal of the other impurities from the gas is very effective.
In addition, because the tars resulting from gasification contain roughly 15% of the chemical energy resident in the gasification feedstock, our process recycles them back into the gasifier in a way that ensures they are broken down and no longer form the unwanted compounds.
Synova takes a comprehensive approach to developing cleaner, more efficient waste-to-energy projects.
Together with its technology affiliate Royal Dahlman, Synova has developed a turnkey, four-step solution:
- Feedstock preparation (at a remote location or co-located with steps 2-4)
- OLGA gas cleaning
- Power or chemical production
We typically develop or co-develop projects from the ground up, from sourcing the waste supply and choosing the site to securing offtake agreements; from connections and permits to arranging technology and construction agreements; from operations and maintenance to issuing debt and equity. Projects are typically structured so that no investment is required from the municipality (the waste supplier) or industrial host (the off-taker).
Modular designs are available for independent power, and can be leveraged for custom industrial applications or CHP designs. Royal Dahlman provides the OLGA® kit—and MILENA®, where applicable—and we source the balance from established suppliers. Each unit in the kit is proven at scales equal to or greater than the scale of the first projects, for many years under industrial conditions.
Good for the Environment
Synova takes waste conversion beyond what’s possible with solid waste separation - by recycling the residual, which usually goes into dumps or landfills. The results include cleaner air and water.
Synova systems reduce greenhouse gas. Dumps and open landfills emit methane, a greenhouse gas considered 21x as bad for the atmosphere as CO2. This methane translates into 1.0 tonne of CO2 - equivalent per tonne of waste. Some sanitary landfills capture and flare their methane emissions or use them for landfill gas power, but fugitive emissions remain a significant problem.
Diverting residual waste from dumps or open landfills to a Synova system eliminates these fugitive emissions, and the biogenic fraction of the resulting syngas directly offsets energy from fossil fuels, with an offset that is 2.0x to 1.5x that of conventional competitors. In Southeast Asia, for example, the net effect is a 1.1-1.4 tonnes of CO2 - equivalent greenhouse gas saved per tonne of waste diverted.
Synova systems are good for our water as well as our air. Most landfills (and virtually all illegal dumps) fail to contain their “leachate”, the liquids that leach out from waste solids over time. Without expensive construction to contain it, leachate can pollute water tables and streams—especially where waste is deposited in a low-lying area, like a canyon or a hole dug into a rice paddy or field. The Synova system, by contrast, keeps waste out of the situations that lead to leachate contamination of a community’s fresh water.
Synova systems also fight the problem of fugitive plastic. Once plastic (or other waste) enters our system, birds, vermin, wind, or rain cannot sweep it into waterways. The waste doesn’t get a chance to escape. There are currently five “gyres”—massive floating agglomerations of plastic particles—in our oceans. Three-quarters of the plastic in those gyres comes from Asia—where tipping fees are often too low to justify the construction of sanitary landfills or conventional waste-to-energy plants—a situation uniquely suited to Synova’s solution.
Finally, Synova’s systems avoid the misuse of land. A Synova plant requires considerably less space than a landfill to process the same amount of waste.