Environmental Laboratory
35
The analytical framework for pyrolysis of biowaste used at EBRI, showing the main stages (circles) and products (rectangles), and the analytical processes used at each stage.
are generally best turned into biochar because of the low loadings of contaminants in the fi nal products, whereas low-quality feedstocks are better suited to bioliquid or biogas, because clean-up by liquid–liquid separation, distillation or downstream processing is a necessary part of producing them”.
A relatively new development in processing technology is so- called ‘intermediate pyrolysis’, whereby the feedstock is placed on a moving bed, she adds. “This allows a high degree of control over the process temperatures and times, making it possible to fi ne-tune the conditions to optimise the desired products”.
Quick initial analysis –
Combining the right methods To properly understand the potential of biomass and other organic waste requires an in-depth study of their chemical composition, says Dr Nowakowski: “You can’t simply get away with applying a single analytical method!”. In fact, his understanding of this aspect extends beyond his research, because he also has overall responsibility for the wide range of analytical equipment at EBRI.
One of the fi rst steps when understanding the potential of a new material, he explains, is to carry out a thermal degradation study. This involves heating a small portion (about 10 mg) up to about 750 °C in a thermogravimetric analyser and monitoring how the mass changes as the temperature rises, giving the researchers an initial idea of its volatile content and solid residue. At the same time, the gases released can also be sent straight to a detector using a technique known as evolved gas analysis, again to provide a fi rst impression of what the sample contains.
More information on the products obtained from thermal degradation is then obtained by micropyrolysis–GC–MS. This uses what is in essence a miniature version of the full- scale pyrolysis equipment, with a gas chromatograph–mass spectrometer fi tted to the outlet, confi gured to analyse the vapour-phase products. The research team at EBRI have two such ‘pyroprobe’ systems, with the one they use the most being a multi-shot micropyrolyser from Frontier Laboratories partnered with a Shimadzu GC–MS.
The advantage of this setup, says Dr Nowakowski, is its speed – “in just an hour, you can complete the preparation and analysis of a test sample, and get an idea of the vapours that could be obtained from the feedstock”, he explains. By adding an internal standard, the amounts of given products can be quantifi ed, and a preliminary assessment of product yields obtained, he adds.
The next steps depend on the outcome of those initial investigations, says Dr Nowakowski, but they will often employ elemental analysis, or TOC analysis (using a Shimadzu instrument) to fi nd the ‘total organic carbon’ present in the sample. Another method useful at this point is calorimetry to fi nd the heating value. “Both these techniques can be useful in discussions with clients who might be wondering whether it’s worth simply burning the biowaste to release its energy content”, he says.
Anitta Xavier (Research Placement Student) injects a biomass sample into a Frontier Lab micropyrolyser for direct transfer to the Shimadzu GCMS-QP2010 SE system.
Detailed analysis of the product mix
When it comes to more detailed analysis, the team turn to a range of chromatographic techniques to cover every possible combination of feedstock type, mixture complexity, and analyte chemistry.
• GC–MS/FID, by splitting the column outfl ow and sending it two ways, combines the compound-identifying capabilities of MS with the quantitative performance of FID. There are two such systems at EBRI, both Shimadzu – one with a one liquid autosampler for investigating bioliquids, and the other with a headspace-confi gured ‘pyroprobe’.
• GC–FID (gas chromatography–fl ame ionisation detection) offers simpler and more accurate quantitation than GC–MS, and is used for quick analysis at every stage of biowaste processing. At EBRI, there are a total of six Shimadzu systems that are ready to go with different chromatographic columns, plus two systems that also have capability for TCD (thermal conductivity detection). This is used instead of FID when the analytes don’t contain a carbon–hydrogen bond, making it suitable for analysing permanent gases such as hydrogen, carbon monoxide, carbon dioxide, oxygen and nitrogen. One of these GC–FID/TCD systems has a high-temperature injection port for analysing the heaviest hydrocarbons.
• GC–BID is another system at EBRI that’s tailored to gas analysis, and uses Shimadzu’s BID (barrier ionisation detector), which offers much lower detection limits than TCD for permanent gases.
• HPLC (high-performance liquid chromatography) is the standard method for separating gram-quantities of complex liquid mixtures, and there is a Shimadzu system at EBRI used for analysing aqueous phases from the pyrolysis process, especially organic acids.
As is clear from the above list, Shimadzu systems are a big feature of the labs at EBRI, with over 12 instruments in total. “Having the equipment from the same manufacturer means that we can use the same software and the same analytical processes – which is good both for productivity and training”, says Dr Nowakowski.
And, says Dr Nowakowski, this equipment and expertise is shared with academic institutions, R&D centres and industrial partners at home and abroad – such as the Biochar CleanTech Accelerator. “Doing this allows us to exchange scientifi c knowledge, build teams for larger-scale research proposals, and most importantly focus on applied research”, he explains: “By carrying out such ‘proof-of-concept’ studies, we can make big strides towards product certifi cation and commercialisation”.
EBRI’s impressive array of analytical equipment supports is also available to young researchers, he adds: “We have links with many academic institutions from the UK and Europe – all of whom can apply to use our equipment”, he says. “So at any one time, we might be hosting several Masters and Ph.D. students, based here for anything from a few weeks to several months, and getting the benefi t from our instrumentation”.
Biochar as a soil improver
and polymer additive So what projects is Dr Nowakowski currently involved with?
One project with clear benefi ts on the ground, he says, is a collaboration with Birmingham City Council. This involves generating a biochar-based soil improver from the large amount of tree and shrub cuttings that the council produces from the parks and gardens that it maintains. Called the ‘Urban Biochar and Sustainable Materials Demonstrator’ project, the cuttings are taken to the council-run Cofton Nursery in Longbridge (Birmingham, UK), and fi rst screened to remove leaves and other compostable material. The larger more woody material is shredded and pyrolysed on-site in a unit installed in a shipping container, yielding biochar. This is used in various projects locally to improve soil structure and boost plant growth, while also incorporating the carbon in a form that is not readily biodegraded, and so providing a role as a ‘carbon sink’.
Nowakowski explains that EBRI was closely involved in optimising this setup: “At the outset of the project in 2019, we investigated the potential for using biochar in wide range of applications. We did quite a bit of large-scale work to fi nd the optimum process parameters to produce larger quantities of biochar”, he says.
Another use of biochar that Dr Nowakowski’s team is investigating relates to its use as a fi ller in plastic composites, used (for example) in 3D printing. This is relevant because, as he explains, biochar isn’t always 100% carbon: “Depending on the feedstock and process conditions, cold spots can arise in the biochar, which can trap small amounts of low-volatility compounds such as polycyclic aromatic hydrocarbons, which are toxic. These would normally remain bound to the biochar, but if you’re using it as a fi ller in plastic, which then ends up being heated during processing, it could release these chemicals and cause a safety issue”.
WWW.ENVIROTECH-ONLINE.COM
Page 1 |
Page 2 |
Page 3 |
Page 4 |
Page 5 |
Page 6 |
Page 7 |
Page 8 |
Page 9 |
Page 10 |
Page 11 |
Page 12 |
Page 13 |
Page 14 |
Page 15 |
Page 16 |
Page 17 |
Page 18 |
Page 19 |
Page 20 |
Page 21 |
Page 22 |
Page 23 |
Page 24 |
Page 25 |
Page 26 |
Page 27 |
Page 28 |
Page 29 |
Page 30 |
Page 31 |
Page 32 |
Page 33 |
Page 34 |
Page 35 |
Page 36 |
Page 37 |
Page 38 |
Page 39 |
Page 40 |
Page 41 |
Page 42 |
Page 43 |
Page 44 |
Page 45 |
Page 46 |
Page 47 |
Page 48 |
Page 49 |
Page 50 |
Page 51 |
Page 52 |
Page 53 |
Page 54 |
Page 55 |
Page 56 |
Page 57 |
Page 58 |
Page 59 |
Page 60 |
Page 61 |
Page 62 |
Page 63 |
Page 64 |
Page 65 |
Page 66 |
Page 67 |
Page 68
