FEATURE
SUSTAINABILITY IN AQUACULTURE Water conservation may be the key
S
by Paul B. Brown, Purdue University, Department of Forestry and Natural Resources, West Lafayette, Indiana, USA
ustainability is a term increasingly used to describe innovation in food production systems in general and aquaculture systems specifically. The more sustainability is discussed, the more we realise how complex this goal can be. One of the more interesting aspects of the environmental component of sustainability is water, which, by definition, is an important consideration for aquaculture. However, the goal of sustainability demands a broader consideration of water resources than simply providing a medium for fish and shellfish culture. Population increases and changing food habits are placing significant demand on food production systems. Between now and 2050, increases of 60-100 percent over current food production levels have been projected. The limiting resource in food production will be freshwater. Currently, food production, harvesting, processing, distribution, storage and presentation to consumer demands approximately 70 percent of the total global supply of freshwater. Using current approaches, there is not enough freshwater to
Table 1: Interpolated water footprints for aquaculture feeds (m3/t)
realise increases in food production of 60-100 percent above current levels. Future food production systems will need to consider the demand for freshwater as a critical component of sustainable food production. At first glance, water and nutrition may not appear related. However, demand for water has been related to the water required to produce feed ingredients. Thus, the dietary formulation and associated water required to produce each ingredient contribute to the water footprint. The more carnivorous species in aquaculture have the lowest water footprint because dietary formulations contain a high percentage of fishmeal and fishmeal requires relatively little water to produce, process and distribute. Species using high concentrations of fishmeal have water footprints lower than other species. Overall water footprints for mandarin fish and gilthead seabream are 88 and 500 m3/ton of fish produced, respectively (Pahlow et al. 2015, Table 1). For more omnivorous species, water footprints can be over 2000 m3/t. Commodity feed ingredients (soybean, corn, wheat, canola, groundnut, lupin, cassava, etc.) require significant water resources during their production, processing and distribution cycles and use of those ingredients in diets increases the water footprint of that species. There is significant variability in the water footprint of common feed ingredients. Data in Table 2 are the total global average water footprints for several commonly used ingredients in aquaculture feeds, and not reflective of
Table 2. Total water footprint of selected feed ingredients (global average, m3/t) Ingredient
Species Grass carp
2,200
Barley
1423
Common carp
2,350
Canola meal
2270
Indian major carps
1700
Cassava meal
1878
Nile tilapia
2300
Corn
1222
Channel catfish
2000
Corn gluten meal
12,534
88
Cottonseed meal
860
Atlantic salmon
1850
Groundnut meal
3272
Rainbow trout
1500
Lupin kernel meal
2607
Milkfish
2450
Rice bran
754
Barramundi
1100
Soybean meal
2524
Atlantic cod
650
Soy protein concentrate
1779
Gilthead seabream
500
Sunflower meal
3960
Red drum
2150
Wheat
1826
Whiteg shrimp
1700
Wheat bran
855
Mandarin fish
From Pahlow et al. (2015)
From Pahlow et al (2015)
30 | March 2018 - International Aquafeed
Table 3. Total water footprint for production of various animal products (m3/t) Product Beef
15,415
Sheep
10,412
Goat
5521
Pig
5988
Chicken
4325
Egg
3265
From Mekonnen and Hoekstra (2012)