The composition of the main process outputs from pyrolysis include:
· Pyrolysis oil - this accounts for 5% to 20% of the initial weight of the inputs. Fourier-transform infrared spectroscopy (FTIR) and XRF chemical analysis techniques have been used to check the components of the resulting oils and have revealed a non-toxic, mainly water composition. The oils gather on the heat exchanger and are washed off every 15 minutes with water and detergent, before being discharged to sewer. The detergent breaks down any fat, oils and grease (FOG) preventing this causing an issue in the sewer distribution network. A future development for the technology could be to collect the oil and convert it to liquid fuel for heating applications, but as the yields are very low and its heating value is low, this has not been a focal point for the innovation team as yet.
· Syngas – this accounts for 10% to 20% of the initial weight of the inputs and is released mostly during the pyrolysis stage, but also during combustion. It is mainly comprised of carbon monoxide (CO), methane (CH4) and carbon dioxide (CO2), but also contains trace amounts of micro-pollutants including volatile organic compounds (VOC’s), nitrous oxides (NOX) and sulphur dioxides (SOX). The raw gas is washed in our patented water screen filtration system, which removes the majority of these micro-pollutants, which are subsequently flushed to sewer. The syngas is then compressed and stored for use as and when required. The act of combusting the gas at 1,900°C, via the air inlet valve of the home boiler, enables the energy stored in this material to be released to power the boiler. This chemical reaction also changes the composition of the gases enabling them to be safely released to air via the boiler exhaust. This exhaust is colourless and odourless and falls well within the parameters of a normal boiler exhaust gas composition.
· Char – this accounts for 70% to 80% of the inputs. This is the main fuel source of the HERU. The material has a good calorific value and therefore provides a lot of heat energy when burnt. X-ray fluorescence (XRF) and X-Ray Diffraction (XRD) chemical analysis have both revealed non-toxic components, which make it safe to handle.
· Ash – this accounts for 1-3% of the initial weight of the inputs inputs. The ash results from complete combustion of the char in HERU. The chemical analysis of the ash shows it is non-toxic and of inert composition. This is also washed to sewer.
In summary, the emission outputs include:
· A sewer discharge - which mostly contains water (about 48 litres per cycle, compared to a washing machine which uses around 50 litres per cycle) as well as pyrolysis oil, particulates and very tiny amounts of micro-pollutants from the water screen filtration system. It also contains inert ash and detergent. The detergent helps break down any fats, oils and grease from the oil, whilst the inert ash helps balance the pH, particularly in sewerage network. This emission has been tested as being safe to discharge to sewer .
· An air emission – the air emission is expelled via the household boiler exhaust. It arises from pyrolysis and combustion and has been processed by both the patented water filtration system and boiler. It has been thoroughly tested as being safe for release to air without posing risk of harm to human health or the environment and falls within the parameters of a normal boiler exhaust gas composition. It is both colourless and odourless.