We need to talk about poo

Like most of you, until recently I had never paid too much attention when I went to the toilet. I did my business, pressed the flush and never saw it again. Out of sight is out of mind. When I was living in Rwanda I heard from friends about a German man who no longer flushed and instead used a bucket. My immediate reaction was to laugh, and then laugh some more. When I met Jan, the man in question, I laughed yet again at his idea. How could that be sensible? Does it not stink and attract flies? After a few months I visited his house and saw his toilet. I was surprised that it looked pretty normal and that there was no smell and no flies. In the end I moved in with Jan and was able to become a 'bucketeer' rather than the 'flusher' I had been before (and unfortunately am again) for a few months. The system was extremely low-tech, essentially a bucket and sawdust:

When the bucket was full it was emptied into a compost heap that heats up to around 60 °C, killing any pathogens in it.

So why am I writing about my intimate experiences with a bucket on a blog about farming? Every day we each empty around 15 grams of nitrogen into the toilet, whilst this doesn't sound much, it adds up to 5 kg per year. Recalling from my previous post that globally we each use 15 kg of nitrogen fertiliser of which 50 % is wasted, you can see that we are throwing away a resource that could be used to grow a considerable portion of our diet.

After a few months on the compost heap, mine was ready to fertilise the coffee crop that I will be drinking next year:

Before sewers were developed, most of the human waste cities produced was returned to the land. Doing so allowed Chinese farmers to farm the same land for four millenia and in Tudor England Gong farmers would empty latrines and transport the 'night soil' to the fields. Doing that had it's drawbacks, mainly because it was very effective at spreading disease. Incredibly, 1 million people in India are still being paid to empty latrines by hand. Society has benefited massively from the development of sewers, but they are not the optimal way to deal with our waste. As well as all the nutrients lost, flushing the toilet uses a lot of water - around 10,000 litres a year which is around 25 % of our water use. This isn't just a waste of water, but it also makes retrieving the nutrients from the sewage more difficult as they are so diluted. Putting it into perspective, every day the water and nitrogen we waste could grow about 3 kg of potatoes.

The nitrogen cycle of the UK. The top right arrow labelled '???' shows just how much nitrogen is being wasted. (And no I don't have a scanner)

You can see in the diagram above that a tiny part of the nitrogen we eat does end up back in the soil for crops to use. This is as sewage sludge though which is very different to compost. We put all kinds of nasty substances into the sewer system and these end up in the sludge - it's not a great idea to start adding heavy metals to farmland. Speaking from personal experience (it used to be dumped close to my house) it also stinks since it doesn't have the correct carbon:nitrogen ratio like a compost.

Precious little has been written about recycling human waste in the scientific literature. Geographers have written about it recently but seemingly microbiologists and agronomists have not. As a result, we have little idea of how to handle our waste safely while maximising its value. I am 99% certain that a system as simple as Jan's will never catch on widely here in the developed world. Our fecophobia is so severe that people aren't going to be persuaded to swap their flushing toilet for a bucket. What's needed is a radical redesign of the toilet so that it looks vaguely similar but is no longer wasteful. You might have read in the news that people are starting to think about reinventing the toilet, stimulated by funding from Bill Gates. They are concentrating on the developing world where the need for sanitation is the main priority, but hopefully some of them could be transferred here. It would certainly take some savvy marketing to get people to change their habits... perhaps Apple can get behind it and develop the iCrap? There are already some interesting products out there such as this freezer toilet but that still leaves the composting problem. I don't feel completely crazy envisaging a future where we freeze our waste and it is then collected from the kerbside with the rest of our rubbish. Other people have had more barmy ideas like powering robots with it, feeding it to maggots to make food for livestock or even turning it into burgers (you thought horse was bad)!

The recycling of our waste is a perfect example of an old technology that has almost been abandoned but which could substantially improve the sustainability of our farming system. Since I began writing this months ago, some interesting articles have been written by Fred Pearce about a few scientists that are working in this field. The future is looking brighter. In my next post I'll discuss genetic modification which in many ways is the polar opposite - comparatively a very young technology which, although widely used is feared and ill-understood by large portions of society.

 

First, feed your food

I want start this blog properly by discussing crop nutrition – if we want to feed ourselves, we first need to feed our crops. Improving crop nutrition has been fundamental to increasing crop yields over the last century but is reliant on finite resources. Plants require at least 17 elements to grow and a lack of any of them can cause growth to decrease. In this post though I'm only going to discuss nitrogen, as it is the main nutrient that plants require.

Nitrogen is abundant on earth (78% of the atmosphere) but it is useless to plants as a gas and they need help to 'fix' it into forms that they can use. Biologically, this can only be performed by microbes which are either free-living in the soil or live inside specialised structures in plant roots. To achieve maximum yields however, crops need supplementary nitrogen. We began to supply this two centuries ago, when deposits of guano were found on tropical islands. This was inherently unsustainable since guano is a fossil resource, ultimately having come from life that lived thousands of years ago. A century later, the Haber process was invented, allowing us to fix nitrogen chemically. In the last 50 years, applications of N fertilisers have increased 20 times to 100 million tonnes a year, or 15 kg for every person on Earth. This makes it a major source of fixed nitrogen on Earth as the diagram below shows. The massive increase in the supply of nitrogen has allowed the population to blossom.

The nitrogen and carbon cycles. The orange part of this diagram represents the fixed nitrogen that we add to the world each year and what happens to it. The blue in the left half is what occurs naturally. The right hand side shows how the carbon and nitrogen cycles are linked. Borrowed from Gruber and Galloway 2008

This has come at a considerable cost however. The Haber process is extremely energy intensive and as a result the price of fertiliser is sensitive to changes in energy prices. One tonne of ammonium nitrate now costs around 3 times what it did a decade ago and this price pressure is not going away. Further, much (as much as 80%, often 40%) of the nitrogen applied to fields never ends up in crops. Rain washes it into the water table polluting our water supply and causing eutrophication of rivers, lakes and even oceans. In Cambridgeshire, the tap water can a contain higher concentration of nitrates than are ever found in plants! Some soil microbes eat fixed nitrogen producing nitrous oxide, a powerful greenhouse gas that also promotes the formation of smog, which in turn is damaging to crops. When the nitrous oxide is eventually washed out of the atmosphere by rain it fertilises nutrient-poor habitats allowing grasses to replace heathland, resulting in the local extinction of species. Across the EU nitrogen pollution has been estimated to cost £55-£280 billion a year (£110-560 per person), of which agriculture is responsible for 70% . This means that the financial cost of nitrogen fertilisers is double the benefit gained from using them! We can carry on as usual, but there has to be a better way.

The visible effects of nitrogen pollution - most is much harder to see. Courtesy Sasha Trubetskoy

Organic agriculture eschews the use of chemical fertilisers and so has to rely on a combination of nitrogen-fixing plants (crops like beans and peas and cover crops like clover), manures, composts and fish meal. These all have their own problems too. Beans and peas only leave behind a relatively small amount of nitrogen in the soil after they are harvested. The nitrogen in composts and manures has to come from somewhere, meaning that a larger area of land needs to be farmed to supply the nutrients. Ultimately, it seems likely that a fair chunk of the nitrogen in organic systems does still come from the Haber process – if cows on one farm are fed food from conventional farms, then their manure can be used on organic farms. Fish meal is probably the most wasteful source however, since producing it requires the wholesale destruction of marine ecosystems. The extra nitrogen that agriculture relies on has to come from somewhere, and currently organic agriculture cannot supply it. Considering this, it's not surprising that some 'enterprising' people have produced supposedly organic fertilisers that in fact contain chemically fixed nitrogen.

One of the simplest ways to improve the situation would be to encourage the growth of free-living nitrogen-fixing bacteria in soils. They already fix a small amount of nitrogen without us doing anything to encourage them. At the moment we know very little about how we might go about this, but obviously any increase would be helpful. It is likely that we could breed crop varieties that stimulate the growth of the bacteria and also identify bacterial strains that fix more nitrogen. More radically, we can try to genetically modify cereals to form symbioses with bacteria in the same way that legumes do. This may not be as difficult as you might imagine, since cereal roots already form symbioses with fungi to supply phosphates, and it was this mechanism that was hijacked by nitrogen-fixing bacteria in legumes to allow the symbiosis to form. A group at the John Innes Centre have recently been awarded £6 million to research this. It will certainly be worth keeping an eye on their results.

A more complex solution is to make more efficient use of the nitrogen that we apply to crops and ensure that more is recycled rather than flowing straight through the system as it does now. We need to establish how to keep nitrogen in the portion of soil that roots can access for longer. Often, nitrogen only is applied at the beginning of the growing season, meaning some is leached by the time the crop needs it. Controlled release fertilisers have been around for decades and have been shown to decrease leaching and increase yields. Evidently the cost of these to the farmer often outweighs the benefits though, or more would use them. In the same way that we could improve nitrogen supply by encouraging bacteria that fix it, we could use nitrogen more efficiently if we were able to decrease populations of microbes that 'eat' nitrogen. How we can do that though is a mystery at the moment, but I'll eventually get round to discussing how we can try to manipulate soil microbes in a separate post.

Most radically, we will need to change the way we waste nitrogen every time we go to the toilet. I think this is so important that it'll deserves it's own post!

The challenge

Our agricultural system is facing many challenges and in the coming decades will have to change significantly. It can't have escaped your attention that before long there will be 9 billion people on the planet, who will each eat more than an average person today. Filling all those bellies without destroying the planet in the process is going to be difficult! To make matters worse, as oil becomes more scarce and expensive, agriculture will have to step up and produce more non-food crops such as timber, cotton and biofuel. With climate change thrown in to the mix, it's not surprising that the situation has been described as 'a perfect storm'. The wheat price over the last 30 years demonstrates this isn't just hype:

Admittedly, the graph is not adjusted for inflation, but as The Economist note food prices are rising in real terms for the first time in decades.

To give you some idea of the scale of the challenge this 2010 paper with 54 authors identified one hundred questions of importance to the future of global agriculture. Each of these opens a Pandora's box of further questions, many of which are beyond the scope of my interests and so will be ignored. While the social aspects of agriculture cannot be ignored, I am both more interested, and more qualified to discuss the scientific aspects.

I'm currently studying for a PhD in potato agronomy, but my interests are much broader than this relatively specialised field and in this blog I want to discuss the bigger picture. Here I will float ideas for how we can use science to improve agriculture. In this post, I will set out what challenges our current systems faces and use this as a framework for my future posts.

Having spent six months in Rwanda in 2011 (covered in Cafe Mzungu) and now spent a year learning about potato farming in the UK, I've seen first hand the two extremes of global agriculture. You don't need to be an expert to spot the difference:

Neither of these systems can remain as they are today. In the developed world our food production is industrialised and most of us are completely detached from food production. There is nothing inherently wrong with this, and indeed moving away from the land allowed us to do so much else with our time. There is a problem however when food production is overly reliant on unsustainable inputs which also damage the environment. At the other end of the spectrum, billions live in poverty toiling daily just to subsist. Agricultural development is the first step in improving livelihoods – once people produce a surplus they can afford to send their children to school and invest in their land. Currently there is a lack of access to mechanisation, quality seeds and fertiliser, as well as knowledge of how to farm efficiently.

Fundamentally the factors which limit agricultural productivity are land, nutrients, water, pests and disease. These are all in part influenced by the genetics of the crop, but also by the environment in which it is cultivated. I will try to tackle both these aspects in my posts. The importance of the weather can't be ignored as the current drought in the USA demonstrates, but since there is little we can do to improve it other than decrease greenhouse gas emissions, I will largely ignore it.

Ultimately, I'm interested in sustainable intensification – producing more with less. Some people think this an oxymoron but hopefully they can be proven wrong. Genetically modified crops and organic agriculture are often thought of as polar opposites, but I don't subscribe to this view and think that combining the two will be essential. I disagree with many of the ways that both of these systems operate in the developed world at present, but the potential of using them together to reduce inputs and increase yields is huge. It would be better to integrate the best parts of both rather than having two systems moving in opposite directions as is occurring today. GM can provide intensification, while organic principles can help to create a more sustainable system. Some things I'll cover along the way are how to turn shit into gold and how crops can kill weeds. Eventually I'll try to tie everything together to produce my 'farm for the future'.

Finally, just to explain the name – I decided on 'farming geek' a while back after seeing how 'geeks' managed to completely win the argument with anti-GM protesters who were trying to destroy an experiment at Rothamsted. The 'geek' part originally came from Mark Henderson's Geek Manifesto.