(215n) Life Cycle Assessment of the Gasplasma Process: An Innovative Waste Management Option

A growing environmental concern of waste management drives new research toward the identification of low impact waste treatment and disposal options. Life Cycle Assessment (LCA) can be used as a tool to provide information about the environmental impact of these waste disposal methods. We performed an attributional Life Cycle Assessment with system expansion using GaBi 6 LCA software (PE international) for an advanced thermal conversion technology called Gasplasma. Refuse Derive Fuel (RDF) is fed to the innovative core of the Gasplasma process: a plasma reactor follows the gasification of waste in order to obtain an efficient cracking of problematic tars and highly polluting compounds of the raw gas. The high purity syngas is suitable, after cleaning, for electrical power generation in a gas engine. Electricity, together with the stable vitrified plasma slag and the steam from heat recovery, constitute the valuable products of the Gasplasma process.

Advanced Plasma Power developed a pilot plant of the Gasplasma process and supplied process simulation data of a commercial scale plant. We collected, organized and grouped those data for the life cycle inventory.

We performed the hot spot analysis of the Gasplasma process analysing the environmental impact of each unit of the plant. This study takes into consideration the impact categories as defined by CML (Guineè, 2002). The hot spot analysis shows that each unit contributes differently to the environmental impact depending on the type of indicator considered and also depending on the emission and the indirect burden.

The two units of the Gasplasma process that show the most marked impact are the flue gas to stack and the quench that is the cooling unit of the gas cleaning section. The flue gas to stack contributes to the Global Warming Potential for 85% of the total plant burden whereas the effluent emitted from the quench increases the fresh water toxicity, the eutrophication potential and the acidification potential by 60%, 44% and 12%, respectively.

The burden of the gasifier and the plasma is due to the high amount of energy required to produce oxygen and electricity supplied to these two units, respectively. Sodium hypochlorite and urea productions, supplied to the syngas and flue gas cleaning sections are the main contributor for the ozone layer depletion (95% of the total burden).

We also tracked the energy input and output of all activities. This analysis reveals the high primary energy requirement for the production of pure oxygen supplied to gasifier and for the production of electricity supplied to the plasma. The two major energy outputs from the plant are the electricity produced in the gas engine but also the sensible heat of the hot flue gas released to the atmosphere at high temperature.

We performed a sensitivity analysis, considering the marginal electricity production technology. The marginal technology was assumed to be a Combined Cycle Gas Turbine plant with natural gas. The GWP of the Gasplasma process is 20% lower in this case, compared to the scenario with the electricity grid mix (electricity production weighted on the base of the UK specific percentage from the different sources).

References

J. B. Guineè, Handbook on Life Cycle Assessment, Operational Guide to the ISO Standards, (Ed.) 2002, Kluwer Academic Publishers, Dordrecht.