Knowledge for better food systems

FCRN Blogs

Integrated agriculture and aquaculture: an option to mitigate climate change?

September 14, 2015
Miguel Astudillo

This post is written by Miguel F. Astudillo and co-authors of the work presented, which is based on findings in a recent paper published in the International Journal of Life Cycle Assessment. Miguel is a former member of the Oxford Silk Group (University of Oxford) and has been a member of the FCRN since 2011. He is currently pursuing a PhD in consequential life cycle assessment at the University of Sherbrooke (Quebec).

As ever, we’d welcome your comments this blog and the questions it raises – just log in to the FCRN website with the password and user name you used to sign up (contact us if you’ve forgotten them) and then post at the bottom of the blog page.

You can get in touch with Miguel via FCRN member messaging by clicking “send message” on his profile page, (note you will need to be logged in) or by emailing him at m.astudillo@usherbrooke.ca.


Before synthetic fertilisers were developed, farming relied on the circulation of nutrients to maintain crop yields. One ancient method of achieving this was the integration of agriculture and aquaculture (IAA) especially in China and Japan.

IAA can take many forms, but historically one of the most successful was the integration of silk production and aquaculture among the dykes and ponds of the Asian Pearl river delta where mulberry trees were grown on dykes to feed silkworms. The organic residues from the production of silk cocoons were added to the fish ponds, boosting phytoplankton production. A poly-culture of carp in different trophic levels fed on the phytoplankton and detritus. The farmers drained the pond once a year to harvest the fish and move the lake sediments onto the land to fertilise the mulberry trees and bushes. The integrated system produced fish, silkworm cocoons and a small quantity of vegetables.

Today the dyke-pond-silk system has almost completely been replaced by more intensive monoculture of species such as eel and terrapin (reared for various purposes, including for food). However, it is often cited as an example of efficient IAA as it sustained high productivity and high human population densities over centuries, without reliance on synthetic fertilizers or fossil fuels. We decided to conduct a study to examine the greenhouse gas emissions arising from this system to see if it was a more resource effective way of “recycling” organic waste. Of particular interest were nitrous oxide and methane emitted on-farm, both gases that are seldom included in carbon footprint studies of aquaculture (although there are exceptions, see 1, 2). Since these systems are also very labour intensive (involving arduous tasks such as moving pond sediments), we also wanted to estimate the embedded emissions in food imports to the system - we wanted to see how significant these were as a proportion of overall emissions.

The results (see 3) were surprising. Organic residues in a poorly oxygenated and highly eutrophic pond bottom decompose anaerobically into methane, resulting in carp production with a carbon footprint four times higher than that of intensive production of fish of similar value such as tilapia. Emissions attributable to silkworm cocoons were also much higher than the values we found for intensive silk production. The greenhouse gas emissions embedded in the additional food consumed by farmers accounted for 11-22% of the total emissions burden.

The results of the study raise questions about the suitability of these types of systems as a model for climate change mitigation. Although this particular form of IAA is no longer practised and uncertainties are potentially large, other systems, which are not strictly integrated, also employ pond fertilisation. Around 6.6 million tonnes of bighead and silver carp are produced annually in China, often with organic pond fertilisation. To put this observation into perspective: the total annual output of beef is about 68 million tonnes. The emissions from aquaculture fertilised with organic waste are potentially large and deserve more attention.

                                        Image: Astudillo et al (2015)

The metabolic energy needs of the physical tasks were also considerable (an additional ~ 1600 Kcal per day for men and ~1300 Kcal/day for women, on top of baseline metabolic requirements), and, as noted, resulted in additional greenhouse gas emissions from food imports into the system. These emissions associated with labour are high enough to suggest mechanisation may not necessarily result in an increase of greenhouse gas emissions, although this ultimately would depend on how diets change (if at all) following the introduction of mechanisation. Other “indirect” effects of mechanisation such as the impact on human health and the concomitant change in provision of health services could also affect the greenhouse gas emissions balance.  On a methodological note, change-oriented approaches such as consequential life cycle assessment are the “life-cycle method” that study changes in production systems rather than the attributional approach we adopted here. An interesting article discussing the strengths and weaknesses of these two approaches can be found here.

The study only covered one of the issues related to aquaculture; a more complete analysis should address concerns such as freshwater eutrophication and impacts on human health. One positive aspect of IAA systems is that they require less fossil fuel and don’t rely on wild fish capture, the latter a critical issue in the constantly growing aquaculture production. On the negative side IAA systems that “recycle” waste from intensive livestock production can increase (in orders of magnitude) the concentration of E. coli in fish guts, which is a potential source of faecal cross contamination. It can also create reservoirs of antimicrobial resistant bacteria (see 4, 5), raising concerns about the re-usability of waste from intensive livestock production. On a positive note, the use of silkworm pupae in aquaculture is more promising, as they are currently underutilised and it has proven to be an effective substitute for fishmeal.

Finally, we recall that LCA or carbon footprint studies should be compared with caution, as methodological differences can substantially affect the results. For instance very few life cycle studies of modern aquaculture account for greenhouse gas emissions from the resulting organic residues. This is less of an issue when comparing different intensive aquaculture practices, because emissions from organic residues are probably similar. However, differences in whether these are included or not can considerably bias comparisons with studies where these are included in the assessment, such as the integrated systems we have studied, or with terrestrial livestock systems.

References:

1.        Aubin J, Papatryphon E, Van der Werf HMG, Petit J, Morvan YM (2006) Characterisation of the environmental impact of a turbot (Scophthalmus maximus) re-circulating production system using Life Cycle Assessment. Aquaculture 261(4):1259–1268.

2.        Phong LT, de Boer IJM, Udo HMJ (2011) Life cycle assessment of food production in integrated agriculture–aquaculture systems of the Mekong Delta. Livest Sci 139(1-2):80–90.

3.        Astudillo, Miguel F., Thalwitz G, Vollrath F (2015) Modern analysis of an ancient integrated farming arrangement: life cycle assessment of a mulberry dyke and pond system. Int J Life Cycle Assess.

4.        Zhang R-Q, Ying G-G, Su H-C, Zhou L-J, Liu Y-S (2013) Antibiotic resistance and genetic diversity of Escherichia coli isolates from traditional and integrated aquaculture in South China. J Environ Sci Health B 48(11):999–1013.

5.        Petersen A, Andersen JS, Somsiri T, Dalsgaard A, Kaewmak T (2002) Impact of Integrated Fish Farming on Antimicrobial Resistance in a Pond Environment. Appl Environ Microbiol 68(12):6036–6042.

Comments

Peter Thompson's picture
Submitted by Peter Thompson (not verified) on

An interesting post Miguel, while emissions may be a problem the traditional system has important lessons in resource management and offers value in educating people in the nature of ecosystems.

Aquaponics is frequently put forward as a new method of IAA, but while succesful in small scale and high value (western) urban environments has yet to make it's mark, perhaps due to the high financial and manufactued capital it requires. Working to commercialise vegetable production for the mass market from aquaponics, emissions (unless from renewable sources) are also a barrier to sustainability. However with integrated renewables and innovations in sustainable fish feed we should be close. Projects to date appear to have sacrificed either fish yield or plant yield to deliver the other and thereby challenge the financial sustainability of the systems.

We are in the construction process of just such a system, it would be interesting to find out if anyone is interested in looking at the life cycle analysis of the project as a whole.

Miguel Astudillo's picture
Submitted by Miguel Astudillo (not verified) on

Thanks for your interest. Indeed aquaponics is an interesting concept. When we did the literature review we did not find much on LCA of aquaponics, but I had a look and there's some work that has been done recently. An aquaponic system studied in Baltimore (http://dx.doi.org/10.1016/j.aquaeng.2015.07.003) spent quite a lot of electricity and propane heating the water but I'm sure that can be substantially improved with better design. The changes on efficiency as the system scales are also important, we can not compare aquaponics with mature technologies without considering that aquaponics is comparatively "under development".

Best, Miguel 

Wenbo's picture
Submitted by Wenbo (not verified) on

Hi Miguel,

Thanks for this interesting study. Yes the dyke pond system in China was famous and it was assumed with high ecological efficiency in resource use and it is still being seen as a model for recycling economy in China, actually now there are still some integrated aquaculture systems such as duck-fish system exist in China and other countries such as Thailand.

A few years ago (2011) I followed Prof. Peter Edwards on an epic journey in Pearl River Delta and Guangdong province visiting all kinds aquaculture facilities, we tried very hard to find any existed DPS or any remains of it, but we were totally failed. One local fisheries officer told us there was a small DPS museum, and when we found that museum in a large park, only ruins of that museum left.

The disappearance of DPS was primarily due to the high land cost in Pearl River Delta, now this area is one of the most prosperous area in China, the land/pond rent per hectare per year is at 10,000-20,000 USD, the low intensification level and low economic return of DPS is fatal.

According to the ‘agriculture involution’ theory, the DPS system can absorb large amount labor in the limited land area which was very important – large number population and limited arable land were the major problems for ancient Chinese society. However, today the labor surplus is disappearing in China, the labor productivity becoming more important, I don’t think there is any chance the DPS will come back.

Best wishes,

Wenbo

John Kazer's picture
Submitted by John Kazer (not verified) on

Wenbo, that was a very interesting account of changes in China.

I would be interested to hear opinion regarding other smallholder systems elsewhere in China or other countries - will the same logic of changing labour density and land value eventually apply?  That is, smallholding will become uneconomic compared to other land uses?

Miguel Astudillo's picture
Submitted by Miguel Astudillo (not verified) on

Hi Prof. Zhang

That must have been an interesting trip! Prof. Peter Edwards have a prominent role demystifying the DPS. I don’t think either that the DPS system will come back to that region, soaring land prices are indeed incompatible with low-input aquaculture. It is however a pity that they haven’t kept any historical record of it. Another challenge that smallholder aquaculture is facing is hydropower development (e.g. the case of the Mekong basin http://www.pnas.org/content/109/15/5609.short). Incidentally dams in tropical regions are another source of anthropogenic methane emissions. Development economics is beyond my area of expertise, but as labour productivity increases (e.g. mechanisation) the distribution of wealth becomes an issue unless the economy grows steadely, something that, many argue, is unsustainable. I think the latest report of the FCRN about efficiency touches on some of these points.

best wishes,

Miguel

Theresa Haddon's picture
Submitted by Theresa Haddon (not verified) on

Dear Miguel,

You might like to read the various postings by this group as there are some interesting & relevant posts e.g. No.s 1. & 2.

https://www.facebook.com/groups/birminghamaquaponics/936791499726630/?notif_t=group_activity

1. 

Paulo Marini shared Aquaponics Lab's photo.

2 hrs
[Aquaponics Lab's photo.]
Aquaponics Lab

We believe creating an open source platform for aquaponics management and optimization goes hand in hand with visual, comprehensible and practical knowledge. Therefore we are happy to share our newest infographic on nutrient dynamic in a aquaponics systems. Licensed under: Attribution 4.0 International (CC BY 4.0)

2. 

Adrian Feiler

29 January

Commercial scale deep water bed system, feeding 100 ppl twice a day with all you can eat salad. Cape Eleuthera Institute

[Adrian Feiler's photo.]
[Adrian Feiler's photo.]

Miguel Astudillo's picture
Submitted by Miguel Astudillo (not verified) on

Dear Theresa

Nice infographics and website! (http://aquaponicslab.org/) I'm trying to find a way to introduce a raspbery pi in my life but I haven't found yet how. There are some great opensource tools available, which touches on the point I made before of access to technology and wealth distribution.

best wishes,

Miguel 

Kevin_Hopkins's picture
Submitted by Kevin_Hopkins (not verified) on

Very well done article with great graphics.  I found the LCA results quite interesting and would like to see more of these analyses done on other small integrated aquaculture agriculture systems.  Lastly,  I would like to add a few observations that I have made during my work with  these systems over the last 40+ years.  

1.  Using manure in ponds may not be the best use of the manure if the farmer has access and can afford synthetic fertilizers (urea and a soluble phosphate) to fertilize the pond.  This takes care of the problem with anoxia and, if done properly, uses the fertilizers more efficiently (see work by the PD/A CRSP).  Instead,  the manure is more valuable used on land crops in well aerated soils.

2. Experimental small-holder systems with multiple crops often have extremely impressive results at the start but are unsustainable in the long run because they rely on "free" labour.  But the children are available to help only until the farmer starts making money and they are sent to school.  And few farmers that I have worked with (either in LDCs or developed countries) want their children to become farmers.

3. Integrated small-holder systems can be an effective way to start farms on the way to profitability and a cash economy .  Unfortunately, to paraphrase the late Ed McCoy (an ag economist at Auburn Univ and ICLARM, now World Fish), all too often our development schemes only work as long as the farmers stay poor.

Miguel Astudillo's picture
Submitted by Miguel Astudillo (not verified) on

Dear prof. Hopkins

Very interesting observations, when we looked into the economics of smallholder silk production and the results of World Bank project in India we had a similar impression. As practiced it is incredibly labour intensive (in comparison as the more mechanized Brazilian production) and often relies heavily on the effectively free labour of a family business... Perhaps not their most sucessful project.

Best wishes,

Miguel F. Astudillo

Add new comment

Member input

Plain text

CAPTCHA
This question is for testing whether or not you are a human visitor and to prevent automated spam submissions.