Understandable Earth Science

Archive for the ‘Fieldwork’ Category

Gas sample collection at PACT – Investigating how the CC influences monitoring of the S!

In January 2016, Stuart Gilfillan and I (Stephanie Flude) made the long drive from Edinburgh to Beighton, Sheffield to collect some gas samples from UKCCSRC’s Pilot-Scale Advanced CO2-Capture Technology (PACT) facility. The PACT facility hosts a state of the art, pilot-scale CO2 amine-capture plant that can capture CO2 in flue gases from either a 250kW air/oxyfuel combustion plant (that can burn coal, biomass or gas) or one of the two 330kW gas turbines also hosted at the facility.

The PACT Core Facility entrance and the amine capture absorber and desorber columns.

As we are Earth Scientists, rather than Engineers, we are researching reliable means to trace the fate of CO2 once it has been injected below ground for geological storage. As part of that research we are investigating how the captured CO2 itself can be used as a geochemical tracer. This means I have spent much of the last couple of years tracking down sources of man-made CO2 to sample, and swapping my usual field gear – walking boots, waterproof coat and rock hammer – for steel toe capped shoes, hi-vis jackets, torque wrenches and high pressure hosing. We wanted to collect as many different types of CO2 as possible – from different capture techniques and from different feedstocks, and so collecting samples from PACT was an obvious option.

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Our typical gas sampling equipment – no rock hammers here!

We had arranged to visit while both biomass and natural gas were being air-combusted in the 250 kW plant, allowing us to collect samples derived from two different fuel stocks. We were also hoping to collect gas samples from different parts of the carbon capture system, so we could better understand, and ultimately predict, what controls the inherent fingerprint of captured CO2. For this, we wanted to collect samples of the fuel, the combustion flue gas, the residual gas from the amine absorber column, and the final captured CO2:

pact-schem

Schematic of our ideal gas sampling strategy.

The staff at PACT were very keen to help us collect this range of samples, but early discussions raised some problems with how to collect the samples. The PACT facility had been designed incredibly efficiently, with multiple gas analysis instruments housed on site that directly tap and analyse the gas of interest. Unfortunately for us, this efficient design meant that very few external sampling ports were installed on the system – why add sample ports when you can simply flow the gas you want straight to your analyser? After discussions with Kris Milkowski and Martin Murphy, we settled on the idea of collecting samples from the exhaust vent of PACT’s FTIR system, with some supplementary samples collected straight from an external tap on a combustion flue gas pipe.

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Stuart collecting a sample of combustion flue gas from the flue pipe

Once on site, we spent a few minutes working out the best way to connect our sampling equipment (copper tubes, clamps, and gas-sample bags) to the available ports and how to ensure a strong enough flow of gas to sample. We collected from the flue pipe first and then moved across to the FTIR hut. Sampling here was a little more hectic as we had a 4 minute window to collect the sample while the FTIR was purging the gas of interest. We need to be very careful to avoid air contamination in our samples, and standard procedure for this is to purge our equipment with the gas we are collecting for at least two minutes, leaving just two minutes to collect the sample and hook up the sampling assembly for the next sample.

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Stuart explaining our sampling procedure to Kris in the FTIR hut.

By the end of the visit, we had managed to collect combustion flue gas, absorber outlet, and captured CO2 from both gas and biomass feedstocks. With the critical sampling tasks out of the way, we were treated to a tour of the combustion rig by János Szuhánszki.

Janos introducing Steph and Stuart to the combustion rig.

So what happens next? We have spent the last year analysing the samples for their inherent geochemical and isotopic fingerprint.  We have measured the carbon and oxygen isotope composition (δ13C and δ18O) of the captured CO2, and concentrations and isotope ratios of trace noble gases (helium, neon, argon, krypton and xenon) that are present in the captured CO2 stream. The results have just been submitted in a manuscript to the International Journal of Greenhouse Gas Control, so keep an eye open for that in the near future.

A version of this article also appears on the UKCCSRC Blog site.

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So’a Basin Fieldwork, Part 2 – Life on the dig.

Welcome to Part 2 of my blog where I share some of my experiences of carrying out fieldwork in Indonesia as part of the So’a Basin Project . For this post, I am going to focus on the archaeological sites because I know that the workings of a large archaeological dig are a bit of a mystery to most people. To be fair, they are still a bit of a mystery to me – I was there mostly to take geological samples and to help constrain the stratigraphy of the area – but just being on the site, listening to the (very loud) chink of hammers and seeing a stegodon tusk slowly revealing itself a little more everyday was just fascinating.

The So’a Basin Project has various excavation sites scattered across the area, and thanks to the lack of vegetation, some of these show up really well on Google Earth.

Excavations from up high

Google Earth images of some of the excavations in the So’a Basin

The biggest of these excavations is a site called Mata Menge (the middle arrow on the above diagram), and it was near here that the So’a Basin team recently found hominid fossils. The site is a series of trenches, covered with tarpaulin to keep the sun (and very occasional rain shower) off both the workers and the trenches. These were very necessary as temperatures could easily reach 40 °C during the day.

As well as all of the archaeologists, geologists and other scientists visiting the site, the Project hired many people from the surrounding villages to help with the excavation. Each active trench had an experienced archaeologist as a manager, and a number of workers who had been trained to carefully excavate the sediment and rock in the trench, and identify whether a feature was archaeologically interesting (e.g. an artifact, fossil, or change in stratigraphy) and report it to the trench manager, who would note its location and investigate it further.

There were often dozens of people simultaneously using hammers and chisels to excavate the trenches; the first few times you hear this sound it is quite amazing, but it soon develops into a kind of musical background rhythm, that you only notice most when it stops as soon as the whistle blows for lunch break.

At the end of the day, the location of all of the finds (artifacts and fossils) needed to be measured and logged. This was a two-person job with one person taking a levelling rod to each find-location and placing it above each find, and another person manning the Total Station (a combined theodolite and EDM – electronic distance measurement) to measure (very precisely) the location of the find. This could easily add an extra 2-3 hours onto the end of the day if there were lots of finds that day.

Being very pale-skinned and a red-head (albeit out of a bottle), I am used to my appearance drawing a lot of attention when I visit hotter climates. This was exacerbated on my first trip to Mata Menge as I arrived near the end of the season, so was also the unusual newcomer. I lost count of the times I would be taking a sample from the wall of a trench and look up to realise that I had attracted an audience. Sometimes they were wondering if I needed any help, but other times they just wanted to watch whatever I was doing.

The trenches themselves were fairly free of local wildlife, but the wider area was grazed by local cattle and horses, and it wasn’t unusual to encounter a herd of buffalo or other exotic cattle while walking between sites.

Another site, about a 15 minute walk from Mata Menge, is Wolo Sege. It was here that Adam Brumm et. al. found some stone artefacts right below an ignimbrite deposit that was dated to ~ 1 million years ago. As a British, wannabe volcanologist, I was especially interested in this Wolo Sege Ignimbrite, because I don’t often get chance to look at ignimbrites that are younger than 450 million years old. It has everything a volcanologist could want – ash, pumice, accretionary lapilli and crystals (and when I say crystals, I mean shiny, 1 cm amphibole crystals – quite impressive!). The entire unit is about 3 m thick at Wolo Sege (the thickness varies where it has been identified at different sites across the region), and the top 2 m of that is ash (only the bottom part is shown on the photo below). There is a lot of ash mixed in with the pumice, and that, along with all the accretionary lapilli, suggests that there was a lot of water involved in this eruption – whether it was because of a rain storm, or erupting through a lake, we don’t yet know, though.

Wolo Sege Ignimbrite

Photo of the type-section of the Wolo Sege Ignimbrite, referenced to my stratigraphic log, and a close up of accretionary lapilli in the upper ash unit. Can you spot the accretionary lapilli clast in the ash below the pumice?

At the end of the excavation season, the trenches need to be protected to stop any partially-excavated, or as-yet-unexcavated finds being damaged by exposure. Exposed fossils are sealed in a protective gypsum plaster cast, after which plastic sheeting is laid at the base of the trench, and then all the material that has been dug out is used to fill the trenches back in again. This protects and preserves the site ready for the next season, while making it relatively easy to identify how far down you had excavated the year before.

So, that is life on an Indonesian excavation. However, I spent most of my time away from the excavation sites exploring the surrounding countryside, trying to correlate volcanic units, and I will tell you more about that in the next blog.

Mata Menge

Overview panorama of Mata Menge.

So’a Basin Fieldwork, Part 1 – Logistics and Living Conditions

Between 2011 and 2014 I was working at the Quaternary Dating Laboratory in Denmark. For part of my work there, I was involved with the So’a Basin Project, headed by the University of Wollongong, Australia. Some exciting new finds from the project have just been published in Nature along with their age and stratigraphic context and so I thought I would share some of my fieldwork experiences from my time working on the project.

The So’a Basin is in the middle of the Indonesian island of Flores, 75 km east of Liang Bua – “The Hobbit” (a.k.a. Homo floresiensis) cave. The basin contains sediments up to ~ 1 million years old, and has long been known to contain some interesting vertebrate fossils, such as stegodons (ancient elephants), and Palaeolithic stone tools. This makes it an ideal location to try and find fossils of the ancestors of “The Hobbit” (spoiler alert if you haven’t been to read the Nature paper yet – they found some! Sadly, the fossils were found after changed jobs, so I missed all the excitement, but I’m still really pleased that I was able to contribute to this exciting work.)

Basecamp for the Soa Basin Project was in a small village called Mengeruda, where the project rented a couple of houses to accommodate the visiting scientists. Mengeruda was only connected to a (relatively) stable electricity supply a couple of years before my first visit, so the accommodation was fairly basic. One of the houses had the luxury of flushing toilets and running cold-water but if you were staying in the second house and needed the facilities in the middle of the night, you had to treck to a small shed across the yard.

Needless to say, there was no air conditioning, other than leaving the shutters open at night. However, this natural air conditioning system meant that we shared the house with a whole host of creatures. One of the first things I was told on arrival was to always check my shoes for scorpions before putting them on. I didn’t find any nasty beasties in my shoes, but I did find a scorpion in my bed on the first day (many thanks to the ladies who managed the house for pulverising that with a broom for me!). A couple of Huntsman spiders were free roaming in the house, which took a bit of getting used to. While my Australian colleagues assured me that they don’t bite, I am a bit of an arachnophobe, and getting to sleep the first few nights wasn’t the easiest. The best night’s sleep I had, however, was the night the giant gecko hung out in my room. I love geckos anyway, but this one was about 30 cm long; apart from being absolutely beautiful, I knew it would probably eat any spiders or scorpions that came in the room :-).

On my second trip, I managed to avoid close encounters with scorpions and spiders in the house, but did have to get help evicting a giant hornet that started trying to become my roommate (many thanks to Gert for his efficient wielding of a Marie Claire Magazine to evict it). Evenings were often spent sitting on the porch, writing up field notes, where the lights attracted everything from moths to a praying mantis. Unsurprisingly, there are no street lights in Mengeruda, so at night, away from the house, the only light was from stars or the moon. This meant some great views of the stars on moonless nights. Somehow, the local people were able to walk around in the dark without using a torch on  nights like this – I still haven’t figured out how!

Days in Mengeruda started early; even if you were able to sleep past the dawn chorus of birds, dogs and farmyard animals that began around 5:30, it was rare that it was cool enough to sleep past about 6:30.

A truck left Mengeruda, driving to the main excavation around 6:30 every morning. The journey on the truck took ~ 25 minutes, or it was a 45 minute walk with 2-3 stream crossings. The truck would start off fairly full with the just the Project team, but the excavation hired many people from Mengeruda and the surrounding villages, and some of them them would jump on the truck as it passed through the village, so it was often overflowing by the time it arrived at the excavation site. At the end of the day, the truck was often full of fossils, to be studied at the basecamp and later transferred to the Indonesian Geological Survey in Bandung, leaving less room for passengers, so most people walked home.

The track between the village and the excavation presented some amazing scenery. There are hot springs at the end of the village that are used by the local people as a bath (a great way to relax when a cold shower just isn’t enough to scrub off the many layers of volcanic ash, sweat and suncream that can build up during a day of sampling); early in the morning, before the air heats up too much, these produce lots of dramatic steam.

After the springs, the track climbs a hill and then offers wonderful views across rice paddies and rainforest filled valleys towards Ambulobo Volcano; this is even more dramatic early in the day, before the sun burns off the morning mists rising up from the valley. Ambulobo is an immensely pretty volcano, of which I took far too many photos – expect to see more of them in future posts 😉

Ambulobo

Spectacular view looking across the valley to Ambulobo volcano, during the morning commute to the excavation.