PubhD #35: Electronics, Engineering and Chemistry

15 March 17 words: Gav Squires

PubhD returns the evening after Valentine's Day, bringing with it a whole lotta love. Of science...

First up is Basile who is researching agriculture in Tanzania.

In sub-Saharan countries, there’s a huge reliance on agriculture, either directly or indirectly. 80% of the population of Tanzania rely on it and it is the main source of employment. The global paradigm of agriculture is that it has to be productive – people are always interested in increasing yields. Current polices look at being more intensive and using more land. The four main crops grown worldwide are maize, rice, soy and wheat – a very narrow set of crops. This can be problematic ecologically, and it's not helping to feed the world.

Why should we worry about underutilized crops? They can contribute to agricultural sustainability and they use very few chemicals. They increase bio-diversity, are drought resistant and are nutritionally very rich. There is also an economic potential – people know them and will buy them.

The Bambara groundnut is related to the peanut. It’s very high in protein and it requires zero fertiliser as it can take nitrogen out of the air. It flourishes in sub-Saharan conditions and is a very popular crop in Tanzania. With the data collected by Basile and his team, they can assess how important a crop it is for local farmers. It's very popular during Ramadan, so it's a culturally popular crop. It's easy to grow but farmers sell very little of it even though it has a good selling price. In villages with a physical marketplace, trade is much better than in villages without one. If there isn't a local market presence, farmers tend to sell to their neighbours and family. These are people that are in crucial need of income.

The main source of income for Tanzanian farmers is cashews. This crop contributes around 80% of their income and it is all exported. As a crop, it requires a lot of pesticides, so by reducing reliance on cashews there is a positive impact on travel, pesticide use, etc. There is a gender bias in sub-Saharan Africa and Bambara is seen as a ‘woman's crop’. So, is there a danger if it becomes a more popular, profitable crop that men will take it over and reduce the autonomy of Tanzanian women?

Key learning: In 2011, 40% of all global arable land was turned over to either wheat, maize or rice.

Next up is Alison, who is researching plant waste as a potential crude oil alternative.

The chemicals industry in this country employs 214,000 people and makes £55billion per year. Half of the chemicals they create are ‘aromatic’ – the electrons are shared around a ring and are very stable. Aromatic chemicals are found in many common molecules including perfume, fabric conditioner, vanilla flavouring, strawberry scent, herbicides, PET plastic bottles and painkillers. All have the aromatic ring and all are made with by-products of crude oil. We need to find a renewable alternative, and that's where plant waste comes in.

Plant material can contain up to 30% lignin, which is a big aromatic molecule. Now, it's a waste of land, water and resources to grow plants just for lignin. However it can be found as a waste product. In the paper industry it is removed to bleach paper. In wheat and rice crops the stems (straw) contain lignin. It is also a waste product from the production of alcohol.

Then we need to break down the polymer into its aromatic units. This requires a lot of energy as the temperatures need to be between 300oC and 600oC, plus high pressure is required to break it down. This will result in the destruction of some of the things that we want. So, can we use something else instead? Enzymes, for example? It just so happens that there is one that breaks down lignin – laccase. It's found in a fungi that would naturally break down a fallen tree in the woods.

There are different structures between the rings and by using lignin model compounds we can see how the laccase effects these links. In hardwood, we get shorter links, which are oxidised too so the laccase has broken them up. In softwood, the chain lengths were still 75% of their original length so they had not been broken down very well but there was more oxidisation.

In softwood, you could use a second stage in the process to break up the oxidised links. In hexamer, some of the links didn't break down at all. Sometimes a molecule that had broken off was added back on to make it bigger, but this was not helpful. Only certain linkages are broken down so we need a lot of those types of linkages to get lots of aromatic rings in the end. Progress is quite slow at the moment, and there is a lot of work still to do.

Key learning: Hardwood is more reactive than softwood.

Finally, we have Abdul, a last minute replacement, who is researching power enhancement in DC networks.

There are lots of wind farms in this country, especially off the east coast of Scotland. This is green power, which generates no pollution. But how do we transfer this wind turbine energy to the grid? And how can we get it to London some 700km away?

There are two types of transmission lines that can be used, alternating current and direct current. The mains in the UK are AC but your mobile phone charger is DC – it conveys the 240 volt AC into 5 volt DC to charge up your phone. If we transmit from Scotland down to London in AC then there would be a lot of lost energy on the way. With DC, you can send more power with less loss. First, the AC output from the turbines has to be converted into DC, which will be at 400,000 volts. Then when it arrives at the other end, it needs to be converted back into AC.

Faults can occur when cables fall to the ground or when cables touch and cause a short circuit. We have to protect the cables, find the fault and not interrupt supply. We also need to protect the converter and the turbine itself. Can we design the converter in a way to protect the entire supply? The converter that Abdul is working on prevents the current from going the wrong way through the cables and back into the turbine, preventing damage.

How do maintenance find the fault in the cables? Who is going to tell them where it is? Based on measuring impedance you can trace the fault to a section of the whole system and then narrow it down in a matter of weeks rather than the months that it currently takes. This way, the whole system can be protected from a fault. There is no way to prevent a fault. Storms, animal interferences and car crashes happen every few months. We need to be able to locate the fault between the accident happening and the circuit breaker kicking in, this happens within five milliseconds.

Key learning: This new converter and its transmission lines would cost £20million to build.

PubhD returns to The Vat & Fiddle on March the 15th at 7:30 with talks on International Studies, Cognitive Neuroscience and Geo-engineering.

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