Plasma Pyrolysis Or Traditional Incineration?

Waste management is a critical issue facing societies globally. As populations grow and consumption rises, the amount of waste generated continues to increase. There is an urgent need for sustainable and environmentally sound waste treatment solutions.

Two technologies at the forefront of the discussion are plasma pyrolysis and traditional incineration.

Traditional Waste Incineration: A Mature Technology

Early municipal efforts simply burnt rubbish in an open-air burn pile or burn barrel, prompting engineers to develop the first waste incinerators over 130 years ago.

What Is Incineration?

Incineration is the process of burning waste materials at high temperatures in excess oxygen for waste mass reduction. Complete combustion aims to oxidise all organic matter in waste into carbon dioxide and water.

Main Types of Incineration

Over the 20th century, technicians refined the basic incineration concept into a tightly managed waste processing system. Today, there are three main types of incinerators used globally. Each type suits different scales and compositions of waste.

These incinerators include:

Rotary-kiln incinerators consist of a rotating cylindrical chamber that agitates waste and improves exposure to combustion gases at temperatures of 850-1000°C.

Fluidized bed incinerators suspend waste in hot sand, allowing good exposure of waste particles to oxygen at optimum temperatures around 900°C for complete combustion.

Moving grate incinerators are most common for municipal waste streams. Waste moves through the combustion chamber on a grate system with controlled air flows, achieving sufficient residence time and temperatures above 850°C to minimise pollutants.

How the Incineration Process Works

The three incinerators above all employ heat and agitation to reduce discarded materials by over 90% in volume. Computerised control systems moderate the burning process while routing exhaust gases through air pollution equipment.

After incineration, metals and aggregates can be recovered from the leftover ash production, while thermal energy helps create steam to drive electrical turbines. In this way, modern incinerators act as vital hubs in an integrated municipal waste management plan – reducing landfill while generating power from waste.

Potential Drawbacks of Incineration

The basic concept of incineration relies on oxidative thermal breakdown via combustion. This leaves traditional incineration open to several drawbacks:

Acidic gaseous compounds may get released if flue systems fail, posing health risks
Toxic byproducts like dioxins and furans form at lower temperatures
Ash residue still containing hazardous end products requires landfill
High operator training is needed to manage inconsistent waste as fuel

Plasma Pyrolysis: A New Path to Waste Reduction

Plasma pyrolysis offers one compelling alternative to traditional incineration, offering new technology and techniques. Although pyrolysis itself is far from new, conducting the process at ultra-high heats using plasma torches is an innovation that grew from metals processing in the 1960s.

What Is Plasma Pyrolysis?

Plasma pyrolysis uses an electrical discharge to generate high temperatures up to 10,000°C. Waste is subjected to intense heat in an inert atmosphere with limited or no oxygen. This induces thermal decomposition, where complex organic molecules in waste break down into smaller and simpler compounds.

Benefits of Plasma Pyrolysis

There are no issues with inconsistent waste composition, and inorganic compounds melt into an aggregate slag, leaving no hazardous ash residue. What’s left behind is a dense carbon-rich residue similar to charcoal.

The intense heat also breaks down waste into volatile components that vaporise into the gas phase. It results in hydrogen, methane, carbon monoxide, and ethylene production. The generated ‘synthesis gas’ or syngas can then fuel electricity plants while liquid byproducts supply feedstocks for crucial industrial processes.

Barriers to Plasma Pyrolysis Adoption

With such promise, the key question is, why don’t we see pyrolysis systems replacing traditional incinerators? The reality is this technology still faces barriers to widespread adoption, namely:

High capital costs: Building plasma pyrolysis plants requires major upfront investments, which can deter adoption.
High operating costs: These facilities require significant energy input to generate the high temperatures needed. This makes ongoing costs relatively high.
Feedstock limitations: The range of materials that can be processed may be narrower than other waste-to-energy approaches. Pre-processing of waste is often needed.
Policy and regulation lag: Rules governing these new types of facilities often don’t exist yet, slowing development.

Yet with rising waste volumes across developing nations, plus tighter legislation on incinerator air pollution and carbon dioxide emissions, plasma arc processing makes big strides forward each year.

Incineration vs Plasma Pyrolysis: A Comparison

Judging which approach serves better depends greatly on local needs and priorities. But we can highlight a few key comparisons to inform decisions going forward:

Incineration

Plasma Pyrolysis

Atmosphere Difference

– Combustion in the presence of oxygen

– Thermal decomposition in the absence (or limited) oxygen

End Product Differences

– Ash
– Flue gas (CO2, NOx, SOx, etc.) – Syngas (H2, CO, CH4)
– Liquid fuels
– Char/ash

Material Suitability

– Mixed municipal solid waste
– Hazardous waste
– Biomass – Biomass
– Mixed waste
– Hazardous waste
– Complex plastics

Waste Volume Reduction

– 90% volume reduction

– Up to 95% volume reduction

Environmental Impact

– More tar production
– Requires extensive flue gas cleaning to limit emissions – Far fewer acidic gas or particulate emissions
– Huge plasma torch electricity consumption

Energy Recovery Potential

– Limited (heat from flue gas)

– High (syngas can be used for biofuel production and electricity generation)

Safety

– Strict operator protocols minimise risks
– Ash may contain hazardous compounds – Safely processes heterogeneous waste
– Inert slag aggregate byproduct

Economics

– Lower capital costs – Lower operating costs – High capital and operating costs – Valuable syngas and byproducts help offset the price

Maturity

– Well proven, with over a century of refinement

– Rapid recent advances
– But far fewer global installations than incineration

Regulations

– Stringent air emission regulations apply

– Less established regulations

This comparison shows us how the ideal choice comes down to local factors and needs. Developed economies with mature recycling and incineration plant infrastructure may determine that traditional combustion still serves their purposes best.

Conversely, emerging waste industries in developing regions could skip towards pyrolysis systems to deal with expanding landfills and heterogeneous waste. On-site situations with problematic toxic or medical waste may choose small plasma units regardless of other infrastructure.

Drawing Comparative Conclusions

Incineration currently plays a larger role in waste management globally and will continue improving its environmental performance through optimising energy recovery and emissions control. Plasma pyrolysis shows promising potential as an emerging alternative but requires further development and assessment to confirm its sustainability credentials.

What stands clear is that both plasma pyrolysis and optimised incineration will play critical roles in sustainable waste management going forward.

Inciner8’s Advanced Waste Management Solutions

As a global leader in waste incineration technology, Inciner8 provides reliable, affordable, and efficient thermal treatment solutions tailored to specific waste challenges and sustainability goals. Our extensive portfolio includes incineration systems optimised for municipal, medical, and agricultural sectors.

Drawing on our decades of industry experience, we engineer systems equipped with advanced emissions control and energy recovery capabilities that maximise resource recovery while minimising the environmental footprint. Our solutions divert waste from landfills, promote pollution mitigation, and support business operations through clean power and heat generation.

Environment Magazine