What LCA is and why it is so important

LCA analysis is a useful tool to evaluate the impact of a particular process or product in terms of environmental negative effects. The acronym stands for Life Cycle Assessment, and it implies a crucial aspect of these kinds of evaluation: how far back should I go to evaluate the environmental impact of a product, in other words, which is the life cycle?

An example could be:

Let’s imagine comparing two cars, one electric, one that uses diesel fuel. If I just consider their usage, then it’s obvious which is the less environmentally impactful, because, with a standard engine, CO2 is directly emitted into the atmosphere, meanwhile the impact of the electric car is almost 0.

But let’s look further back in the supply chain of these cars, and let’s consider other factors like the impact of gathering the resources, assemblage, and distribution, also, let’s look at where the energy used by the electric car is coming from. We can see that if the energy is produced by burning fossil resources like oil or charcoal, then the impact of its usage is almost comparable with that of traditional cars.

An LCA consists of four stages:

    1. Definition of the objective and scope
    2. Life cycle inventory: definition of input and output of the process, as well as wastes and emissions
    3. Impact assessment: all the inventory data are converted into a few numeric indexes that refer to specific environmental impact (global warming potential, usage of land, eutrophication of superficial water bodies…)
    4. Interpretation of the results: find out which are the main hotspot of the process and find possible solutions. 

LCA is carried out on all kinds of processes, and if we want different studies on the same subject to give comparable results, we need a standard of reference, and this is why LCA is regulated by ISO.

 

LCA of oyster production in Italy

The paper of today deals with the evaluation of two different production systems for oyster farming in Sacca di Goro in Northern Italy, already responsible for the production of 10% of Italian oysters (Crassostrea gigas).

In the current scenario, in the farm the oysters’ life cycle lasts around twelve months starting from already hatched seeds purchased from a producer in France, the two crucial steps are prefattening (8 months) and fattening (4 months). The alternative scenario, that the researchers want to evaluate, is the local production of seeds, which would avoid the external purchasing (local supply chain), and that would imply extra 4 months in the life cycle.

The selected FU was 1kg of fresh oysters (about twelve oysters of commercial size), and the aim was to evaluate a cradle-to-gate life cycle. The SBs were slightly different for the two processes, and was broader in the alternative scenario, including also the impact of seed production.

 SBs used in LCA of oyster production in Goro under the two proposed scenarios: the current scenario (purchasing seed from France, on top); and the alternative scenario (local nursing and hatching, on the bottom). Figure 3 of the referenced article

Types of LCA:

The evaluation of the environmental impact, after performing the inventory and process subdivision, was carried out with two different methods

Eco-indicator® 99-H:

A method of evaluation that considers indirect potential risks in three different categories:

    1. Human health: that has Disability-Adjusted Life Years (DALYs) as a unit, that stands for the days of life lost over the overall population.
    2. Ecosystem quality:  that has Potentially Disappeared Fraction (PDF) as a unit, that can be interpreted as the potential fraction of species of vegetation that has a high probability of disappearing.
    3. Resources: measured as MJ of surplus energy used for gathering the resources.

For each of these indicators then, are available sub-categories like Human health-climate change, or Resources-Fossil fuels…

ReCiPe midpoint (H) v.1.12

That considers the actual direct impact of the process measured in different categories, only four were reported as the main contributors:

    1. Climate change (Kg CO2 eq)
    2. Terrestrial acidification (Kg SO2 eq)
    3. Marine and freshwater eutrophication (Kg PO4 eq)
    4. Water depletion (l)

Results

Which is the environmental impact of oyster production, compared to other aquacultures?

Aquaculture of mollusks (like oysters, mussels, and clams) is in general very convenient because they’re a good source of high-quality proteins, and do not require additional feeds (unlike crustaceans). Oyster’s production specifically does have a positive effect on the ecosystem, by long-line structures acting as spawning and nursery ground for many species, improving ecosystem diversification, and reducing the effects of intense phytoplankton blooms (effects not included in this LCA).

From the results of ReCiPe analysis, the researchers confirmed that oyster production is more sustainable in respect to other aquacultures, similar in terms of CO2 emission to the farming of mussels, but with a lower eutrophication potential.

Title

Climate change (kgCO2 eq)

Marine and freshwater eutrophication

(kgPO4 eq)

Terrestrial acidification

(kgSO2 eq)

Oysters

1.85

1.38 × 10^-3

9.29 × 10^-3

Seabass

11.00–17.00

180–240 × 10^-3

50–80 × 10^-3

Rainbow trout

2.24–13.62

4.04–60.36 × 10^-3

10.43–40.72 × 10^-3

Seabream

3.67

98.86

21.61

Seabass

3.18

91.03

18.85

Turbot

6.02

80 × 10^-3

50 × 10^-3

Salmon

2.16

49 × 10^-3

20.4 × 10^-3

Table report of the impact of 8 different aquacultures, including oysters production in Italy. Re-elaboration of data coming from table 5 and table 6 of the referenced article

Which are the main hotspots from the environmental point of view, in the two production systems?

From the Eco-indicator method, no significant differences were found in the two production systems, and the environmental impact of both scenarios were almost superimposable, with the impact of barges, non-reusable wooden cassettes, and plastic baskets for fattening, being the major contributors.

Comparison between environmental impacts of transport from France and local seed production (LCIA: Ecoindicator®). Figure 5 of the referenced article

It is worth mentioning that the researchers did not compare the two production systems of seeds (local and in France) but considered only the transport of purchased seeds for the current scenario. And just by considering this analysis, it is evident that local production has better performances in terms of climate change, water acidification, and eutrophication of land. Not only that but having a completely local production improves the traceability of the final product across its entire supply chain.

 

Full article available here:

Tamburini, E., Fano, E. A., Castaldelli, G., & Turolla, E. (2019). Life cycle assessment of oyster farming in the Po delta, northern Italy. Resources, 8(4), 170.