Biofloc Systems for Sustainable Production of Economically Important Aquatic Species: a review
Keywords: biofloc technology; aquaculture; integrated multi-trophic aquaculture; sustainability 1. Introduction
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biofloc technology; aquaculture; integrated multi-trophic aquaculture; sustainability 1. Introduction According to the Food and Agriculture Organization, aquaculture is one of the food production sectors that offers a golden opportunity to alleviate hunger, malnutrition, and poverty through income generation and better use of natural resources [ 1 ]. With the in- creasing human population, projected to reach 9.6 billion by 2050 [ 2 ], the demand for food is escalating amidst limited natural resources such as water and land required for the continuous production of food. Nevertheless, aquaculture production is projected to rise from 40 million tons by 2008 to 82 million tons in 2050 [ 3 ]. This is probably due to the gradual adoption of semi-intensive and intensive aquacultural practices for the production of economically important aquatic species. However, intensive aquacultural practices are of great environmental concern due to the discharge of nutrient-rich wastewater into the environment. With all these constraints in mind, the development of sustainable aquacul- ture systems should focus more on system designs that permit not only the efficient use of fewer resources such as water, energy, land, and capital but also minimizing environmental pollution and maximizing production and profitability. This would, in the long run, lead to the fulfillment of the Sustainable Development Goals (SDGs), notably SDG 1 (end poverty), SDG 2 (zero hunger, achieve food security, improve nutrition, and promote sustainable agriculture), SDG 8 (promoting inclusive and sustainable economic growth, decent work Sustainability 2021, 13, 7255. https://doi.org/10.3390/su13137255 https://www.mdpi.com/journal/sustainability Sustainability 2021, 13, 7255 2 of 15
for all), and SDG 14 (conservation and sustainable use of water bodies for sustainable development) [ 1 ].
that has attracted the attention of the scientific community and producers for sustainable aquaculture due to (i) zero water exchange, thus permitting efficient use of limited water resources and preventing the discharge of nutrient-rich wastewater into the environment; (ii) reduced artificial feed input (fishmeal), which reduces the costs of production while permitting the inclusion of alternatively cheaper and highly nutritious protein sources, and (iii) natural establishment of microbial biomass that not only purifies water but also enhances the growth, growth performance, and immunity of aquatic species reared in the system. The use of this system in farming practices for the production of crustaceans and some finfish species has been extensively studied [ 4 – 12 ]. The aim of this review, therefore, is to (i) give a brief overview of BFT systems, including operational parameters that affect their efficiency; (ii) review studies that have been conducted on the application of BFT systems for the sustainable production of economically important aquatic species; (iii) highlight the economic aspects of BFT systems, as well as their drawbacks and limitations, and recommend management aspects of BFT systems for sustainable aquaculture. 1.1. Biofloc Technology According to the National Agricultural Library Glossary (United States Department of Agriculture, North Bend, WA, USA), BFT is defined as ‘the use of aggregates of bacteria, algae or protozoa, held together in a matrix along with particulate organic matter to improve water quality, waste treatment and disease prevention in intensive aquaculture systems’ [ 2 ]. In other words, BFT relies on the principle of nitrogenous waste recycling by several microbial species (bioflocs) in the system while improving water quality and the growth performance of the reared aquatic species. Heterotrophic bacteria within the system take up ammonium as a nitrogen (N) source for their biomass, thus resulting in a decrease in ammonium/ammonia in the water to non-toxic levels. This process is, however, faster than the nitrification process carried out by autotrophic nitrifying bacteria due to the faster growth rate of heterotrophic bacteria. Figure 1 shows a general overview of the BFT system. Certain factors that affect floc formation (mixture of microorganisms) and water quality in BFT systems are discussed below. Sustainability 2021, 13, x FOR PEER REVIEW 3 of 16
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