Earthworm Cast Carbon Storage (ECCS)

Earthworm Cast Carbon Storage (ECCS) 

by R.J.B in Japan

Almost all global green plant NPP of 218 Gt C/yr (Ref.) is ultimately processed by earthworms with net 5-18 Gt/yr potentially stored in soil representing 99.95% of CCS compared to artificial CCS of ~0.0085 Gt C/yr ^[1] {quoting total of just 31.5 Mt of CO₂ per year = 8.5 Mt C/yr}. The importance of soil carbon (vs. plants or microbes) is realized in Figure 1 shown below:

[The above figure’s above-ground vegetation and below-ground SOC are corrected from Crowther et al.’s (2019: 3) original that had just 1,500 Gt SOC although their figure 2C tallied to 4,595 Gt SOC, now doubled for terrain to ~10,000 Gt SOC! See – Blakemore 2019, 2020].

Globally, soil contains ten times more carbon (>10,000 Gt SOC) compared to above-ground vegetation (~1,000 Gt C). Human emissions of ~10 Gt C in CO₂ each year are just one thousandth of total soil C! All atmospheric carbon (860 Gt C in CO₂) is  re-cycled through the intestines of earthworms via leaf litter & root exudates in approximately (860/218 Gt C NPP =) 4 yr cycles. To store the 4 Gt annual atmospheric accumulation excess C requires ceasing human emissions by 40%, or by increasing NPP from 218 to 222 Gt C/yr – a 1.8% increase in plant productivity and soil storage.  Soil is the solution to CO₂ driven climate change as the only practical & painless CCS.

[My latest revision (Ref.) amends this to say: “Thus the problem of atmospheric CO₂ accumulation is inability of the biome to fix and reabsorb due to biomass clearing/grazing/poisoning/burning and wanton destruction of topsoil with critical decline of earthworms“. So a remedy is more to prevent topsoil loss rather than just try NPP increase].

Comparatively, 4p1000.org global ambitions state: “If we consider 4 per mille in the top 1m of global agricultural soils, SOC sequestration is between 2-3 Gt C year^− 1, which effectively offset 20–35% of global anthropogenic greenhouse gas emissions” – Ref.). Blakemore (2018, 2020) found annual NPP to be 218 Gt C/yr on land alone, and this is all ultimately processed by earthworms in the soil on an annual basis too. Yet earthworm populations are depleted by -83% on average in agrichemical fields (Blakemore 2018a), thus restoration increase would return these numbers to their ideal potentially increasing the ECG/ECCS benefits five fold.

Crosschecking: Earthworm surface casts dry weights average 105 t/ha/yr (Lee 1985: tab. 18) and subsoil casting may be equal to give 210 t/ha/yr; with 26 Gha soil mantle this is 5,460 Gt/yr. Mean carbon content of 4% and C:N ratio of 11.4:1 (Lee 1985: tab. 21) gives 218.4 Gt C/yr (equal to the entire annual NPP) plus about 20 Gt N/yr. This seems reasonable for a global SOC total of >10,000 Gt C giving N total of around 1,000 Gt N in worm-worked topsoil humus. Glomalin, a tightly bound glycoprotein, may add an extra ~27% to almost all soil carbon budgets, and is particularly abundant in volcanic soils of Japan and Hawaii (Ref., Ref.), to give 284 Gt SOC/yr; and earthworm cast calcite adds another 1 Gt/yr for total of 285 Gt SOC/yr (figured below). Although much is also respired annually (estimated as up to 200 soil C/yr – Ref. with some studies not accounting for litter and none allowing for annual earthworm calcite). [Note: Published C:N ratios are not yet affected by glomalin that is usually un-measured in SOC totals].

As another cross-check on casting rates, a global earthworm dry biomass of 15.2 Gt (Ref.), if on average a worm processes its body weight of soil per day, would give 15.2 x 365 days = 5,548 Gt dry soil, or just about the same as the 5,460 Gt/yr casts calculated above.

Total casting rates above- and below-ground at Rothamsted Research station under pasture were at least 115 t/ha/yr and in UK woodland about twice this at 240 t/ha/yr (Ref.). In their plots with organic FYM fertilizer, the calcite-producing Lumbricus terrestris occurs at about 14 worms/m² while none are found in chemical plots (Ref. – this data differs to that published, as I already notified the author in 2018 – fake Ref.). Sparse data is available for Japan, but Hatai (1931) reported 281.7 t/ha/yr and Watanabe (1975) found Amynthas hupeiensis & Eisenia japonica (as redescribed by Blakemore 2011, 2012) produced surface casts at a rate of 38 t/ha/yr and the latter species has calciferous glands. The mean casting rate of ~160 doubled for sub-surface casts to 320 t/ha/yr and times Japan’s new area of 0.17 Gha (Ref.) gives 54.4 Gt casts/yr; at 4% SOC = 2.2 Gt C/yr exceeding Japanese annual emissions of 0.3 Gt C/yr by more than seven times (and this is 72,000 times greater than Tomakomai’s CCS of 0.00003 Gt C/yr!). In extensive boreal/permafrost regions another calciferous species-complex of Eisenia nordenskioldi is widely distributed (see Blakemore 2013).

Earthworm Calcite Granules (ECG), a trivial component, greater than Global CCS

Calcite (crystaline CaCO₃) contains about 12% carbon. Calcite may be added to soil organic totals as a minor but valid earthworm exudate mainly from atmospheric CO₂. For exaple, Batjes (1996: tab. 6) reports a median value of 722 Gt C (range of 695–930 Gt C) reserves in “inorganic” carbonate mostly in the upper 1 m compared to about 1,500 Gt C SOC giving a SIC:SOC ratio of about 33:66% or 1:2. This may be doubled for terrain to give a new global total of around 1,444 Gt carbonate SIC. As new global soil area is 26 Gha (Blakemore 2018b) then this 1,444/26 Gt/Gha rate gives 55.5 t C/ha in carbonate, on average, although sources of this may be partly from fossils of molluscs or other organisms rather than only from that produced by earthworms (Ref.).

Much higher values than Batjes (1996: tab. 6) are from Monger et al. (2015) to just 1 m depth with “inorganic carbon as soil carbonate (~940 PgC) and as bicarbonate in groundwater (~1404 PgC)” and Lal (2019: tab. 1; 2020) who says: “global SIC (primary and secondary carbonates) stock is estimated at 1237 Pg to 2-m depth [plus tab. 1 an extra 321 Gt in humic soils] and an additional 1404 Pg as bicarbonates stored in ground water”. These later figures total ~2,962 Gt which, if doubled for terrain totals >5,924 Gt SIC/DIC.

The next photo shows the amount of calcite granules produced in just about a month by a single Lumbricus terrestris earthworm (from Canti 2007: fig. 2).

Versteeg et al. (2014) reported that Lumbricus terrestris exuded 0.8–2.9 mg CaCO₃ worm^-1 day^-1. With this earthworm’s population varying from 2–62 worms m^-2 this equates to precipitating 2–261 kg carbonate C/ha/yr, a potentially significant contribution (of median 130 kg/ha/yr) to carbon sequestration. This is supported by a UK report (Mark Hodson www.reading.ac.uk/web/files/ta/ASE_calcite_and_earthworms.pdf) that summarizes earthworm casts contain calcite produced in high amounts averaging 98 kg C ha^-1 yr^-1 that is approximately 0.1 t C ha^-1 yr^-1. As UK has 10 million ha of agricultural land (arable, managed grass or woodland) now doubled for terrain to about 20 million ha, then this rate would total ~2 Mt calcite C/yr that is about 2% of UK’s annual C emissions.

Several other field worms also increase calcite as my PhD study showed for combinations of nine earthworms where calcium (Ca) was raised by up to 12–19% for Pontoscolex corethrurus and by Aporrectodea trapezoides in both test soils, less for the other species (Ref. 1994: tabs. 2.3.22–2.3.23). The same exotic, tropical P. corethrurus species from Amazonia was found to have a greater proportional effect in Indian soils (Ref.: tab. 8).

In comparison to BECCS/CCS, S/ECCS is entirely safe and essentially cost-free with no penalties since composts are economical & benign, earthworms work tirelessly for free, and non-farmed land is simply set-aside to regenerate naturally. As global agricultural land is about 5.1 Gha (now doubled for terrain to 10 Gha by Blakemore 2018b), then a similar rate of earthworm calcite C production as Hodson’s value of 0.1 t C ha^-1 yr^-1 would total ~1.0 Gt calcite C/yr that adds +12.5–33% to typical organic SOC sequestration quoted as 0.3 to 0.8 t C ha^-1 yr^-1 or 3–8 Gt C/yr in these managed lands. Figures are imprecise estimates based upon the limited available information but show another potential key influence of earthworms on the local scale having environmental import at global scale (just as Darwin already told us 140 years ago).

Charles Darwin spent much of his life researching earthworms (Darwin 1881) and was the first to report on their casting rates, their importance to archeaology, and their production of calcite.

Fossilized calciferous glands of L. terristris were named as Arion kinkeli Wenz, 1956 & A. hochheimensis Wenz, 1956 (see – Blakemore 2016 “Cosmopolitan Earthworms”). These ECGs, once mistakenly thought the product of snails (see Canti 2008), are now used for palaeological and archaeological radiocarbon dating helping us to understand past climates (Ref., Ref., Ref.). As Canti points out, heavy predation of earthworms by various animals & birds means that there is a constant redistribution and recycling of the granules in the biosphere. [And this raises another question of just how much fertilization of land by bird droppings is constituted from earthworms?]. Why we are not up to our armpits in calcite is due to steady dissolution rate as Hodson showed. This is true for all decomposition on oxygen-rich land, compared to under water and in the ocean where decomposition is limited.

Soils started to form more than 2.6 billion years ago (Ref., Ref.) and Purschke (1999) suggested a primary terrestrial origin of detritivorous Annelida, plus it is inferred that early diversification of (mainly marine) annelids took place at least in the Lower Cambrian (Ref.), so we may suggest annelids are equally likely to have originated on land or in pond mud and subsequently colonized littoral habitats as much as vice versa.

Interestingly, the current best estimate of 1 Gt C/yr earthworm calcite is more than all the solid CaCO₃ in the shells of all marine organisms, estimated at just 0.7 Gt C/yr (IPCC TAR-3, 2001: 198).

As well as producing microbially-active and resilient carbon-rich humus for fertilizer, vermi-composting of manures, municipal & all agricultural ‘wastes’ also increase calcium carbonate compared to regular composing. The three main composters, Eisenia fetida, Eudrilus eugeniae & Perionxy excavatus increased the CaCO₃ content by between 50–500% compared to regular compost, dependent upon feedstock source Ca concentrations (Ref. 2010: fig. 1a). In my 2015 “African Nightcrawler” report, total carbon for Eudrilus eugeniae worked compost comprised 21–28% C with 1.5% inorganic C (as a proxy from 5% Ca) and for field soils the casts of this species had about 1% total C with about a third (0.3%) as inorganic C from the Ca ratio (Ref.: tab. 1). Thus scope for immediate ECCS implementation for rapid CO₂ drawdown is huge since the original sources of the all carbon in earthworms composts & casts is from atmospheric CO₂. Moreover, from carbon and oxygen isotope analysis ECGs are themselves about 50% composed of CO₂ from air in the burrow not from SOC food nor from soil water (see figure on page 50 in Mark Hodson’ 2019 report, https://web.archive.org/web/20191112041749/https://www.reading.ac.uk/web/files/ta/ASE_calcite_and_earthworms.pdf copied below).

From this 50% soil air source information plus the fact that CO₂ concentrates in soil due to microbial decomposition & root respiration, it is possible that ECGs are partly a mechanism to make the burrow atmosphere less toxic allowing oxygen diffusion through earthworm’s cuticle so that it may respire more efficiently – they can breathe easier. This extra oxygen allowance would also benefit soil microbial respiration and thus the rate of organic decomposition. The respiration theory has many proponents since Combaut (1909), McDowall (1926) & Voight (1933) – as reviewed by Robertson (1936). Of all higher Life’s needs, the most critical is the constant requirement for oxygen.

Annual “Worm wash” contributes to loss of Soil Nutrients & Carbon

An unavoidable loss of soil nutrients and carbon occur each year in the bodies of innumerable earthworms washed into streams and rivers (pers. obs.), particularly after flood. Accurate figures are not available, but Atlavinyte et al. (1974) had earthworm population depletion of 4.5–36.2%, with overall average of 2.7 g/m² biomass loss from cultivated lands. This would translate as about 27 kg/ha with half of this (or 13.5 kg) carbon. As global agricultural land is about 5.1 Gha (doubled to ~10 Gha for terrain), wash off loss via riverine transport of earthworm bodies would amount to about 0.135 Gt C/yr. This figure may actually be much higher, at least doubled for non-agricultural lands to 0.27 Gt C/yr. Nevertheless, it is already 10 times more than current best achievements of CCS totals of just 0.009 Gt C/yr ^[1] or BECCS with just 0.0005 Gt C/yr of carbon from CO₂ [2].

Earthworms and other soil fauna that effectively process fixed carbon are depleted by ~80% in agrichemical fields[3]. So, logically and economically, if earthworm populations are restored to their original levels in organic soils as before agrichemical expansion, then the rate may well be five times higher (20% x 5 = 100%), so 0.27 x 5 = 1.35 Gt C/yr. Thus $2 billion irrationally wasted on BE/CCS is much better invested in organic farming to restore sad but effective annual worm-wash plus natural S/ECCS.

An obvious and additional synergistic benefit is better field drainage via worm burrows reduces desiccation, flooding and erosion thus helping to save topsoil and preserve earthworm populations.

Mangroves don’t Matter – “Blue Carbon” is a “Red Herring” (Reminder of CCS Context)

Wasting more time & money are mangroves (part of a Blue Carbon/Marine Misinformation network – Ref.) that are relatively insignificant despite much hype. Their potential carbon sequestration (according to Ref.) is in the order of “1.3–2.0 Mg C ha⁻¹ yr⁻¹” but as they occupy less than 14 million ha (or 0.014 Gha) it gives a potential carbon sink of a measly 0.025–0.122 Gt/yr – less than the annual earthworm wash off. While this too is 10 x the current CCS/BECCS, it is about 10 x less than the realized annual ECG production and just <1.5% compared to the actual terrestrial SOC sink. These 24 authors (Ref.) say mangroves boast 6.4 Gt to 1 m and 12.6 Gt C to 2 m; compared to >8,580–10,000 Gt land-based SOC (Ref.) it is a minuscule <0.1% or a proverbial ‘Storm in a Teacup’.  Being at sea-level their “soils”  (actually marine sediments some, if not all, washed off from proper soil!) gain nothing from terrain. See Kirschbaum et al. (2019) summary of Blue Carbon also the Drawdown Review figures below… 

Commercial CCS/BECCS Failures and Falacies of “Geoengineering” Fantasies

Ignored is earthworm cast recalcitrant SOC humus and calcite C sequestration, the latter in UK at 2 Mt C/yr alone is 60 times Japan’s Tomakomai CCS project aim for 0.03 Mt C/yr and 20,000 times UK’s $3.3 million pilot Drax BECCS scheme trapping just 100 t C/yr (actually zero so far!) but now being upgraded by $6.5 m to allegedly store 5 Mt C/yr from American timber! [The ridiculous economics and environmental damage of this project was recently exposed – https://sandbag.org.uk/project/playing-with-fire/]. The $300 million site at Tomakomai represents a tiny portion of the $20+ billion wasted in CCS each year and just the UK’s likely ~2 Mt/yr free earthworm calcite ECCS is greater than all current global CCS or BECCS achievements in schemes that potentially capture at most 10.5 Mt C/yr (or 0.0085 Gt C) from human emitted CO₂^[1][2] all at huge costs with many failing along the way. Their byproducts (amines, nitrosamines, nitramines, aldehydes, amides) also being human carcinogens and highly toxic to the environment (Ref.) producing yet more chemical contamination. Chemical CCS costs are also enormous: estimated at $600/t CO₂ or >$2,000/t carbon (Ref.) thus it makes neither practical nor economic sense. This is to be expected when chemists, physicists, marketeers or, worst yet, self-styled geoengineers try to understand and meddle in Ecology. Here a new surprise (to all but the rationally cynical): the makers of these toxic chemicals are the self-same as the makers of the biocides that have caused the soil death and, even more ridiculous, the amines are mainly from hugely expensive and CO₂ emitting Haber-Bosch process (Ref.) that contaminates soil, air and water.

Artificial CCS or BECCS at very best could only ever achieve 10 Gt C/yr to offset all fossil fuel emissions. This impossible dream is only 4% of the actual annual 218 Gt carbon capture already realized by Nature that is all ultimately processed, or stored, in topsoil. Loss of this carbon from topsoil is the greater challenge that needs to be faced with the obvious solution – both ecologically and economically – being the restoration of organic farming (which by definition is organic carbon farming). A starting point is recycling of all biotic ‘wastes’ that are currently incinerated or dumped. The only problem with the simple soil solution is that there is no quick profit to be had from natural processes with earthworms doing all the service work for free, however there are great savings in terms of preserving of natural resources and improved health issues. The earthworms work tirelessly and our best hope for survival is to find the proper ways to allow them to do their job naturally. Ridiculous and anti-ecological CCS projects in the power sector would cost upwards of $69-$103 per tonne of CO₂ and BECCS is much worse at $60-$250[4] per tonne costing at least $200–750 per tonne of carbon or well above $3 trillion for all 10 Gt excess fossil fuel carbon emissions each year. Money better spent on organic farms…

S/ECCS is better than BECCS!

But don’t just take my word, check out the latest 2020 Project Drawdown Review (page 13):

Figure above shows soil as greatest most reducible source & by far greatest carbon sink.

Context summary above clearly shows ocean is not a solution (0.4%), neither is fantasy CCS/DAC (1.1% including artificial charcoal marketed as “biochar“). The only feasible way is reducing soil as a source & removing excess CO₂ from air back into the soil sink (98.5%)!

Yet a Better Way

In contrast to CCS, one week’s global emissions shutdown with organic restoration would incur minimal outlay and only a potential 2% GDP reduction of just $1.6 trillion for that year (Ref., Ref.), much less than estimated cost of climate damage and cleanup costs. Pathetic and costly BECCS schemes are even more senseless when using agrichemical biomass crops (GMO corn or cane) that take at least ten units of fossil fuel energy to product just one energy unit of crop (Ref.)!; and if burning yet more wood are beyond ridiculous. (Ditto “biochar” scams by ‘biocharlatans’ that offer zero advantage over proven, conventional compost and many, many penalties, but much short-term profit!). [There is perhaps a place, however, for “biocrap” – the carbonized sterilization of biosolids if toxic heavy-metal burdens are low for addition in some situations]. Science speculation without rationality is fake science-fiction. Much better to rely on science-fact and to grow food organically (with zero or minimal fossil fuel cost) and to freely vermi-compost all wastes for return to the field, as Nature expects. When agrichemical poisons are avoided then mass global extinctions and physical/mental sickness (especially with farmers’ families or their neighbours) are further reduced. [Synthetic fertilizer increases by 10 times and biocide increases by 4 times have accomplished only double crop yields that are more correlated with doubled irrigation (Ref. fig. 7b); at the same time soil loss has escalated: e.g., on average 12 t of topsoil eroded for each tonne of Australian wheat, in some part it is much higher at 200 t lost (Ref.), obviously a trajectory only towards collapse].

Footnote: This week (11^th November 2019) Australia burns, and no-one on any continent can escape critical loss of species, melting ice/permafrost and/or forest/peat fires. At the very least the premiums on insurance (if you can get it) will skyrocket. The main cause, as is admitted by IPCC, is bad agriculture and a massive expansion of non-essential meat-eating. If you burn a tree in Tokyo or Sydney you will be fined several $100s. But your burger is proxy burning 100s of trees in the Amazon or in Indonesia. And Australia, already using up most of its natural forest or grasslands for beef or sheep, is another victim. We have great sympathy for people who are affected by flood or fire but we seem to avoid responsibility by still eating meat. The link is direct and is food for thought: India is mainly non-meat-eating with great food dishes and Buddhists avoid cruelty and killing of fellow beasts. To compensate for all the bad karma & damage, meat burgers should perhaps cost >$100 each as the extravagant indulgence and health/environment insult they truly are (Ref., Ref.).

Overgrazing (as by goats above) depletes already eroding or poisons soils. When crops fail (even for organic/permies) then we all starve… except for the worms. The best & only solution is mostly free Soil/Earthworm CCS (SECCS) – we urgently need more SECCS!

An afterthought study I am now working on shows that if Tasmania alone converted to wholly earthworm-based organic farming it could potentially offset all Australian annual Fossil Fuel CO₂ carbon emissions of about 0.11 Gt C/yr each year for about 10 years. Any progress on other States would contribute to drawdown of atmospheric carbon via plant photosynthesis and SOC storage. As another example, for the UK their entire FF emissions, also about 0.1 Gt C/yr, could easily be accommodated by soil carbon. Details of this study will be notified once published. Please be patient for these interesting results…

Free ditty:-

Mor, Moder, Mull,

Earth will be unfull,

‘Till more Mor is Moder

And more Moder’s Mull.

Foto-joke of Aus-terrier-alia & Tassie as cat food…(not my original idea though):-

(Phots transformed from Irish Wire Haired Fox Terriers, Siamese Cats, and Mice clubs).