Thermal treatment of municipal and biomass wastes. Research of AGH UST scientists

One of the priorities in the field of environmental protection is the implementation of the idea of circular economy (CE). The concept is based on quite a simple premise that the Earth’s resources are limited, and thus we should minimise their extraction and decrease the production of waste. One way to achieve this can be following the 3R principle – reduce, reuse, recycle. The clou basically is to reduce unnecessary consumption, reuse products, and recycle resources from waste. This is how we can cure the problem of insufficient resources on Earth and also reduce greenhouse gas emissions into the atmosphere that cause negative climate changes.

The research team led by Dr Aneta Magdziarz focuses primarily on the issue of organic waste treatment that can be used to extract raw materials for the chemical industry, as well as produce biofuels. The work carried out within the framework of this issue is within the scope of the first Priority Research Area (PRA-1), established as part of the project “Initiative for Excellence – Research University”. PRA-1 is all about the search for sustainable energy technologies, renewable energy sources, and energy storage methods, as well as the development of efficient methods of resource management. Through these activities, the AGH UST wishes to fulfil its obligations towards society by providing knowledge and solutions that are of key importnace for further human growth.

Scientific explorations

How can we recycle valuable materials from biowastes, or how can we transform them into a clean energy source? A good alternative to piling up various types of waste in landfills is, for example, thermally transforming it into products that we can benefit from. This can be done by means of the thermal conversion processes – for instance, torrefaction, hydrothermal carbinisation, pyrolysis, or gasification. The AGH UST scientists focused on the process of pyrolysis of organic waste. Pyrolysis (from Greek pyro – fire, lysis – separation) is a process of thermal decomposition of complex chemical compounds into simple ones, which occurs at high temperatures in inert atmosphere (N2, Ar).

 

 

Technical design of an experiment stand used during research on biowaste thermal treatment

The research carried out at the AGH UST is related to the pyrolysis of agricultural and wood-type wastes. During the research phase of the project, a detailed analysis of the physicochemical parameters of the substrates and pyrolysis products of the studied wastes was carried out w

ith the use of a wide spectrum of advanced instrumental methods. Furthermore, the scientists investigated the way in which the participation of a catalyst influences the efficiency of the process, as well as the quality of particular products. In cooperation with Xi’an Jiaotong University, studies were conducted on the so-called co-pyrolysis of wood waste biomass and rubber waste during the catalytic cracking process. As a result, a decrease in the concentration of phenol in the pyrolysis oil and a reduction in the water content in the products of pyrolysis were achieved.

A necessary condition to receive a research grant was to prepare a publication in international cooperation and to include at least one doctoral student in the research team. In the case of Dr Aneta Magdziarz’s team, there are two doctoral students working on the project. A doctoral student, Małgorzata Sieradzka, MSc; and a doctoral student, Artur Bieniek, MSc. Participation in this project constitutes an excellent opportunity for the two to broaden their knowledge, develop their scientific interests, and form prospective relationships with international partners. Both doctoral students received tasks for the fulfilment of which they are responsible. Artur Bieniek uses numerical methods in computational fluid dynamics to compute the efficiency of pyrolysis products with changing process conditions, that is, temperature, type of carrier gas or its flow rate. For this, he uses the Ansys Fluent program, which is dedicated to scientific issues related to the exchange of heat and mass. Małgorzata Sieradzka performs analyses of the composition of the pyrolysis gas using gas chromatography.

 

 

Magnified structure of biomass and biocarbon
 

‘Gas chromatography is an instrumental method used to analyse the composition of particular chemical compounds in mixtures. To put it briefly, we have a certain gaseous mixture – pyrolysis gas, for instance – and we analyse it in terms of the content and concentration of, for example, hydrogen, carbon monoxide, carbon dioxide, or hydrocarbons. To analyse particular compounds that make up our gaseous mixture, they are carried by a neutral carrier gas (e.g., He) to a chromatographic column, where they are separated on the basis of the so-called time of retention. The column is chosen specifically for the substances analysed. As a result, we receive a chromatogram that shows peaks for particular compounds against the retention time. Those results are then compared with chromatograms obtained during analyses of calibration gases of known composition and concentration’, explains the project leader.

A new lease of life for biowaste

Organic waste can be reused in a number of ways. Another method of recycling is to transform it into RDF (Refuse Derived Fuel). This, in short, is how we started to call alternative fuels from selected waste with high thermal value (14-19 MJ/kg). Such energy sources can be a good alternative to conventional fossil fuels – coal, oil, or natural gas. Furthermore, biowaste is also a valuable source of chemical compounds that can be used successfully to produce cosmetics. An example of such a biowaste material comes from the brewing industry, namely the so-called draff. It is a lignocellulosic material that contains bioactive compounds, including phenols, which attract a great deal of attention from the scientific community, given their wide application scope.

***

The project titled Multicriterial analysis of pyrolysis of agricultural waste biomass, biodegradable wastes, and RDF fuels was funded by a university grant within the framework of the project “Initiative for Excellence – Research University”.