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NAERINGSPH-Nærings-phd

Anaerobic digestion of pyrolysis products

Alternative title: Biogassproduksjon av pyrolyseprodukt

Awarded: NOK 2.4 mill.

Project Number:

317138

Application Type:

Project Period:

2020 - 2023

Funding received from:

Organisation:

Location:

Despite the threat from global warming, global demand for energy is increasing. Biogas offers a flexible carbon-neutral alternative to fossil natural gas and has applications in energy production, heating and as a transport fuel - and even as a simple starting molecule for chemicals. There are several large scale biogas production facilities in Norway and globally, with well established distribution infrastructure. Additionally, the biogas production process offers many advantages in the treatment and stabilization of organic waste. Pyrolysis offers a different approach for creating energy from waste, and can handle many other waste fractions. Pyrolysis is the process of heating materials to elevated temperatures (>300°C) in the absence of oxygen, and creates a variety of energy-rich gaseous (pyrolysis gas), liquid (condensate) and solid (biochar) pyrolysis products. Biochar has many applications and can in some cases act as a "carbon sink" - resetting CO2 emissions - but the complexity of pyrolysis gas and condensate often requires expensive investments to use, for example as fuel. Research has indicated that all of the various pyrolysis products separately may have a positive impact in the biogas production process depending on the amount added. However, condensates from pyrolysis tend to accumulate persistent organic pollutants (POPs). By treating pyrolysis gas and condensate in a biogas reactor, biogas production plants can employ pyrolysis and avoid investment costs related to pyrolysis gas and condensate management, while increasing their biogas production. However, the fate of POPs from pyrolysis condensate in an AD process is unknown, and we still need more research on tolerance limits and process requirements for digesting pyrolysis condensate. The primary objective of this PhD project is studying the link between pyrolysis and biogas production from sewage sludge, to investigate the fate and consequences of POPs in pyrolysis of sewage sludge and biogas production of pyrolysis condensate.

Based on the project results, we now more about emissions from the Biogreen pyrolysis equipment, which can aid in applying for permits for users of pyrolysis equipment. The results provide a foundation of lifecycle assessments and can provide input for environmental policy. From the projects, we know more about biogas production from pyrolysis condensate and the consequences from the persistent organic pollutants present in the condensate.

Modern society produces various types of waste streams. With an increased focus on circular economy and responsible resource management in addition to stricter regulations regarding waste handling, the demand for sustainable waste handling solutions is increasing. Pyrolysis is the thermal decomposition of organic materials in the absence of oxygen. Waste streams that Scanship is exploring for pyrolysis is in particular sewage sludge and digestate, the remaining mass after biogas production (anaerobic digestion). The pyrolysis process eliminates the problem of micro-plastics and several other pollutants in digestate, by converting it into stable char (often called biochar depending on the feedstock) and synthesis gas (syngas). ). While traditional incineration converts all carbon in the digestate into CO2, pyrolysis can store up to 50% of the initial carbon in the char, causing a carbon sequestration effect if used in land applications. Additionally, the volume of the digestate can be reduced drastically, reducing the need for transport. Studies on syngas and the liquid condensate of the pyrolysis has shown that the addition of these to the biogas production process have the potential to increase the yield of methane in biogas (biomethanation), but more research is needed on this subject. To reduce carbon emissions, and even go to negative emissions, Scanship is aiming to provide customers a circular approach where pyrolysis can provide an increased biomethane production and at the same time reduce transport needs for digestate while offering a value-added product through biochar. Ideally, the link between pyrolysis and biogas production could be as simple as redirecting syngas directly into the biogas production tank, improving methane yields and optimizing energy production from the initial substrate. However, more research is needed to know whether this is a realistic option or if there are other possible solutions.

Publications from Cristin

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Funding scheme:

NAERINGSPH-Nærings-phd