Fossilised farts (and other agroGHGs)! Part 2: The expansion of Livestock and the debate around the Anthropocene.

Now, studies by Brook et al. (1996); Schlit et al. (2010); Sowers (2010); Burns (2011); Singrayer et al. (2011) and Wolff (2011) all show ice core records and other proxies (analogues for past environmental records) like speleothem (calcite deposits) to show CH₄ and other GHGs like N₂O over the Holocene (11 ka BP; Sowers, 2010) to 140 ka (Schlit et al. 2010). These records show the link between precessional cycles and CH₄ concentrations; but up until 5 ka, the CH₄ concentration deviated from what is expected due to the precessional cycle. The NH has been at an insolation minima due to the precessional cycle being in a NH negative stage (i.e. the southern hemisphere, SH, has more intense summers and winters).

This discrepancy between expected and observed therefore does not follow the natural process. Now shoot me if you must, but I agree with research put forward by Ruddiman, and I am joining in the argument/debate on the Anthropocene. In an article by Ruddiman et al. in a special issue Holocene published in June 2011 (where some of the other 2011 articles from Holocene are taken) attempts to falsify anthropogenic and natural increases in CO₂ and CH₄. The case states that only one other (stage 11) deglaciation has a similar increase in methane after the initial peak and decreasing tail (which would be due to a natural or at least non-anthropogenic process). All of the records (except stage 11) show a decrease of CH₄ in line with NH summer insolation minima. Stage 1 (our current Holocene/Anthropocene) does not follow this trend. Due to the rise and spread of humans through the globe, the establishment of civilisations and the first age of modernity through agricultural development, Ruddiman et al. (2011) and Fuller et al. (2011) show that it is expansion of agricultural practices of wet-rice farming and livestock intensification which is responsible for the anomalous rise in atmospheric methane contribution. This is significant for this blog as it shows (even among scientists like myself… ok I am only a student) humans have had an effect on the greater environment and the Earth’s ecosystems through a variety of anthropogenic process; relating this to livestock they include deforestation (increasing CO₂) and increased agricultural production (increasing CH₄ and later with the green revolution N₂O). This rise is evident 5 ka; that is why I believe that humans have had a significant impact on the earth before 250 yrs BP, it’s been 5 ka that’s how far the Anthropocene extends. This is shown in the graph taken from Fuller et al. 2011. 

Graph showing CH₄ predicted (NH insolation records) and measured CH₄ in GRIP ice core over time.

The Fuller et al. (2011) article looks at agricultural (pastoral and arable) contributions to prehistoric methane levels, using archaeological evidence to match it to the GHG records. This graph from their article shows the deviation from the predicted methane concentrations from the GRIP ice core. The black square points represent actual methane concentrations. The difference between the two data sets is ‘potentially’ cow farts and other anthropogenic processes (causing the deviation). They go deeper, investigating the spatial distribution of the technologies and knowledge of the more intensive (and greater GHG producing) agricultural techniques over time. Here are some maps showing the expansion of livestock practices:

Southern and Eastern Asia Livestock technique dispersal Fuller et al. 2011

Africa Livestock technique dispersal Fuller et al. 2011 

Southern Asia Livestock technique dispersal Fuller et al. 2011

The increased expansion of these farming practices means that more food was able to be cultivated, for direct food (like rice) or indirect food (like livestock feed).  This archaeological evidence shows the actual distribution of the increasing anthropogenic CH₄ sources. Another integral point (that will be elaborated on in part 3 of Fossilised farts) is the fact that the inter-polar gradient (IPG) between ice core records of CH­₄ concentration in Greenland and Antarctica begin to equate (Chappellaz et al., 1997; Burns, 2011). If for instance the NH boreal arctic polar circumference began to emit greater amounts of CH₄, then Greenland’s ice cores will have a greater concentration of the gas than Antarctica’s cores due to the proximity and difficulty of inter-polar diffusion. The fact that the IPG is levelling out shows that the source is low latitude; agricultural expansion into Africa, Southern Asia and South-Eastern Asia can be an explanation to this. Coupled with greater CH₄ emissions from the amazion basin (due to a stronger SH summer) and other low latitude CH₄ sources; this could explain the 5 ka rise. 

Fossilised farts (and other agroGHGs)! Part 1: The natural sources of methane in the past.

Records of trapped gas (of which some are fossilised farts) come from ice cores. GISP2 and GRIP (central Greenland) and the Vostok cores (Antarctica) show GHG levels fluctuating for millennia; stadials and interstadials (Brook et al., 1996). Focusing on methane and nitrous oxide (nitrous oxide will become increasingly significant during the green revolution and greater use of fertilisers), the role which livestock domestication and increased production has played on levels of those gases has been increasing over the late Holocene, correlating with the increasing human population and complementarily food demand.

Butt (pardon the pun), there are a variety of natural and other anthropogenic process which produce CH­₄ (and N₂O). To add to the debate about when humans had a global effect on the planet, we must be able to distinguish the gases between the various human and natural process, and that’s  where the magic happens…err, the science I mean.

The earth has always been able to regulate the gases in the atmosphere thanks to dynamic equilibrium. A long time ago, in a land quite close to home, early Homo sapiens sapiens lived as hunter gatherers and there was no such thing as an economic crisis. Over the last 140 ka (Schlit et al., 2010), atmospheric concentrations of greenhouse gases has varied naturally (as they have done before human mastery of emitting vast amounts of GHGs) due to feedback processes which are triggered by either external (orbital cycles, volcanic eruptions) or internal (organisms, Dansgaard-Oeschger cycles, Heinrich events, oceans) processes (Brook et al. 1996).

In the prior blogs I (hope to) have shown the main anthropogenic sources of the GHGs methane and nitrous oxide (as well as CO­₂, but due to its greater abundance in the atmosphere and number of sources is hard to quantify what proportion is due to livestock processes). These two gases in particular are good indicators of livestock production and other agricultural process as they can have a signal specific to the process of formation and as natural methane is dependent on the precessional cycle of the earth (explained further in part 2) it is relatively easy to predict and categorise as it increases and decreases in line with the earth’s precession. The main sources of methane come from the humble bacteria. Decomposers, who (as the name suggests) decompose organic matter (dead plants, leaves, bodies…err cow poo or rice stalks, to name but a few) anaerobically (without oxygen) which produces methane.

The best way of removing oxygen from soil (where tonnes of organic matter meet with anaerobic decomposers) is through water-logging/increasing the water table. Like any other organic process involving enzymes; the warmer the environment, the greater the rate of the process occurs, ergo more methane.

More organic matter + higher temperatures + greater water logged soils + decomposer bacteria = a load of natural methane!

The greatest sources of natural methane are large areas on earth (where else?) where temperatures are sufficient to allow decomposition to occur, have large stores of organic carbon in the soil and are highly water-logged. The source of the organic material is the crux of the matter, if it comes from cows stomachs via the rectum (LOL) then increasing the cow population directly increases methane produced from anaerobic decomposition, as well as their farts of course.

Tropical/sub-tropical and boreal (peat land) wetlands are the largest sources of natural methane. Other natural sources include termites, wild fires, wild animals farting, methane hydrate release and oceans (Ruddiman et al., 2011). In the ice core records, the direct correlation between the CH₄ concentration and precessional cycle boils down to the northern hemisphere summer insolation. The precessional cycle dictates the amount of summer temperatures in each hemisphere, governing the seasonal intensity (temperatures/precipitation) and the monsoons. As the direction of the tilt of the earth towards the sun changes cyclically over 22-26 ka (Ruddiman et al., 2011), when the northern hemisphere (NH) is pointed towards the sun when at the same time the earth is closest (the perihelion) to the sun then the NH summer insolation is high, increasing temperatures and precipitation, as seen in speleothem records across the tropics (Burns, 2011). Due to the inter tropical convergence zone (ITCZ) shifting northwards, NH precipitation increases the water logged state of the tropical/sub-tropical rainforests and greater insolation heats and melts permafrost in the boreal band across North America and Eurasia; paving the way for those nasty bacteria to unlock the frozen carbon in the form of the by-product that is CH₄.

You see… all those old-fashioned climate sceptic and climate change deniers are right… it’s not the fault of humans; we just have to destroy all those evil decomposer-bacteria that produce this bad gas, get the Dettol at the ready!

So what is the problem with excessive farting (also burping, urinating and excreting)?

Why is it even an issue worth discussing in a blog dedicated to the world of excrement? Well the fundamental problem we face, not just as a species, but as inhabitants of earth, is climate change. We humans use the planet as our only home, kitchen, garden and toilet. Like any other confined space, when you begin to change the chemical make-up of the gas enclosed in that volume, you begin to change the overall physical, chemical and thermal properties of that gas. In the case of excrement, methane (CH₄) and nitrous oxide (N₂O) is produced through a variety of processes (as is carbon dioxide, CO₂) which contribute to the greenhouse effect (Popp et al., 2010). Carbon dioxide is the most significant anthropogenic produced GHG due to the sheer quantity that is emitted into the atmosphere from human activities.  

However, as I touched upon in the previous post, over 100 years, the same amounts CO₂, CH₄, and N₂O have varying potencies due to their thermodynamic properties. This property is applied as a ration of heat trapped by one unit mass of the GHG compared to one unit mass of CO₂; this is called the Global Warming Potential (GWP) (Pitesky et al., 2009). As it a ratio, CO₂ has a GWP of 1; CH₄ has a GWP of 23 (in the previous post I wrote that the potency of methane was 20 times that of carbon, it was wrong sorry!); N₂O is 296 (FAO, 2006). From this data, it shows how important methane and nitrous oxide produced from livestock production, and in particular from poo, will be an increasing problem, not just as the total number of GHGs (CO₂ and non-CO₂) is set to increase from projected and modelled figures (Popp et al., 2010). In addition, with populations estimated to reach 9 billion by 2055 (World Bank, 2011) and increasing qualities of life reflecting greater demand for meat in the diet; livestock rearing is set to increase; that equates to a whole load of shhhhh… excrement.

The United Nations Food and Agriculture Organisation (FAO) commissioned a report on the impact livestock production has on the planet,Livestock’s long shadow (FAO, 2006). As a whole, livestock (either directly or indirectly) is responsible for 18% of total anthropogenic GHG emissions (FAO, 2006); those figures broken down into individual GHG include:

·  Carbon dioxide (CO₂) 9% of global anthropogenic emissions.

·  Methane (CH₄₎ 35 – 40% of global anthropogenic emissions.

·  Nitrous oxide (N₂O) 65% of global anthropogenic emissions.

·  Ammonia (NH₃) 64% of global anthropogenic emissions.

However, as I will investigate later on in the blog (or further towards the top of the blog), Excretion and everything  does not just play an integral role to GHG emissions, it also plays a vital role in the nutrient cycle, particularly phosphorous and nitrogen. Phosphorous (P), as well as nitrogen (N) in the form of nitrates and other vital macronutrients like magnesium (Mg), potassium (K) and calcium (Ca) are required as well as a variety of other micro nutrients (Robinson, 2004). Phosphorous is often a limiting factor in plant production, due to its vital role as an ingredient in deoxyribonucleic acid (DNA) and ribonucleic acid (RNA), the building blocks of life; and in the Adenine triphosphate (ATP) which is the primary method of intracellular energy release and storage (Biology-Online, 2011), so we can all move, keep warm and most importantly… LIVE! Also, specifically to plants, P is necessary for healthy root growth, vital for the uptake of water and the other nutrients. The role fertiliser plays is significant, and indeed focusing on one of the nutrients, phosphorous, an increasingly important point has surfaced. Livestock (cows for example) need to eat; feed is created from plants; high amounts of land and biomass is required to produce vast amounts of feed; limited land resources dictates more intensive farming methods; greater dependence on higher yields; synthetic fertilisers created to provide the vital nutrients for plant growth; mining of phosphates from a finite source requires large amounts of energy whilst depleting the source.

As you can see, just from scratching the surface, cow (and other animals’) farts and poo pose a more serious problem than the humorous connotations applied to them suggest. Over the next few weeks and posts I hope to show you a greater insight in to the world of climate change, nutrients (re)cycling, pollution, eutrophication, renewable energy and many, many more uses, and subjects, which poo influences.

This blog may overlap with others, in fact it will. A post by fellow GEOG3057 blogger Emma (I hope she is Ok with me using her name), touches on the renewable potential of methane gas from… well cow farts. Another blog dedicated to the debate around biofuels can also shed light on the increasing diversification of energy sources, by another fellow GEOG3057 blogger Yulia. But those topics are for another time!

Next I hope to give you an insight into past methane releases and the relationships between the potent GHG and the atmosphere, looking at palaeo records of methane…essentially fossilised cow farts… Ok well some of the methane was produced by pre-modern time cows farting. Until then… watch those deadly emissions!

References:

Biology Online, 2011, ATP Definition. Available from: http://www.biology-online.org/dictionary/Atp. [Online] accessed 24/10/2011.

FAO, UnitedNations, Food and Agriculture Organisation, 2006, Livestock’s Long Shadow: Environmental issues and options, FAO-UN:Rome.

Pitesky, M. E., Stackhouse, K. R. and Mitloehner, F. M. 2009, Clearing the Air: Livestock’s contribution to climate change, Advances in Agronomy, 103, 1-40 pp.

Popp, A., Lotze-Campen, H., Bodirsky, B., 2010, Food consumption, diet shifts and associated non-CO₂ greenhouse gases from agricultural production. Global Environmental Change, 20, 451-462 pp.

Robinson, G. 2004, Geographies of Agriculture: Globalisation, restructuring and sustainability. Harlow: Pearson Publications Limited.

World Bank, Development Research Group, Human Developmentand Public Services Team, (Das Gupta, M., Bongaarts, J. and Cleland, J.) 2011, Population, Poverty and SustainableDevelopment: A Review of the Evidence, World Bank: Washington D.C., WPS5719.

If you find this sh.... stuff interesting then you might find these blogs interesting to! 

Please check them out, as I try to myself!

Agriculture: Human Health and Earth Health: http://robs-agriculture.blogspot.com/ 

Biofuels: Way Ahead or Blind Alley: http://biofuels-wayaheadorblindalley.blogspot.com/

Fixing Climate Change: http://fixingclimatechange.blogspot.com/

Welcome!

Welcome!

This blog is to inform, amaze, inspire and of course explain the many uses of poo… Now please do not adjust your screens or refresh the page, I did just write poo.

Before we indulge ourselves in the wonders of excretion, understanding of the past is vital to analysing potential solutions of present problems for the future. In this context, methane (CH4) is a significant greenhouse gas (GHG), 20 times more potent than carbon dioxide (CO2) and one way that it is emitted is in the form of cow (and other animal) farts, and the anaerobic decomposition of organic materials, like manure. 

But before all of that! Here is a video that makes light of the fundamental argument that I am making.

Enjoy and I will post again soon!