RAS (ISRAS):

The Future of Aquaculture?

This comment is in response to a good article on RAS posing the question of whether RAS is the future of "fish farming," but my comment encompasses not only "fish," but also shrimp and most other fed aquaculture species. Unfortunately, the CSM article fails to adequately inform regarding the primary economic advantage of recirculating aquaculture production systems. When properly designed RAS systems' have the unique ability to recapture significant amounts of the 70-80+% of aqua feed nutrients and energy that don't actually go into tissues of the species being cultured. This is a unique ability not technically possible in flow through and cage culture systems where nutrients disperse into the surrounding bodies of water.

To be more specific, the future of aquaculture isn't just RAS systems in general,  but it is in RAS systems that are specifically designed to effectively capture waste feed nutrients and use them directly to produce additional marketable product while recovering the value of typically wasted feed investment. In the face of the current peak commodity resource crisis - particularly the confluence of peak petroleum and peak phosphates cost increasing impacts on NPK fertilizer/feed costs, RAS systems inherently lend themselves to be designed to specifically optimize the recovery and profitable utilization of wasted energy and nutrients. Conceptually, RAS systems that efficiently collect and convert waste feed particulates and dissolved nutrients into lower trophic species - filter feeders for particulates and or that use algae or bacteria for dissolved nutrient conversion to be used directly as either algae products, or as filter feeder foods can recover much of the lost waste feed value.

Feeds represent 50-60% of most aquaculture venture production costs - even with the best of feed conversion ratios. As such feed/feed utilization is the single most significant, if not the most economically sensitive aquaculture economic operating cost. Most aquaculture industry feed conversion calculations relate wet weight aquaculture product (70-80% water content) to dry weight feed (9-11% moisture). While convenient for feed use calculations, it is misrepresentative and inaccurate in trying  to understand feed efficiency and economics. If we consider processing losses for example:

 

    - In shrimp the head and shell counts for 40% or more waste/loss of cultured  

      product.

    - In fish fillet production up to 60% of the carcass can be offal/waste. 

In reality the shrimp aquaculture industry (and terrestrial animal producers as well) mistakenly uses dry weight feed to wet weight animal product ratios. The 2:1 feed conversion in say shrimp is really 2 lbs. of dry wt. feed converted to 0.2 lbs. (75-80% water) dry wt. shrimp - then the head of the shrimp is discarded and we are left with a real dry wt. feed conversion ratio of 2 lbs. of dry wt. feed to 0.16 lb. of dry wt. marketed shrimp product - shrimp shell and offal value considered.   Simple math shows that 1.84 lbs. of feed went some place beside the marketed shrimp product. Worse this means that not only did 85-92% of the feed not end up as marketable product, but about 50-55% of the of the operating cost (assuming feed was 60% of the operating cost) was potentially wasted.

In fish production - with often higher offal levels, feed waste and lack of feed use  efficiency can also be very significant.  If we consider an FCR of 1.2 using a feed dry wt. of 11% moisture and whole live fish moisture content of 70, 75, 80% we have 72, 77, 81% of the feed not ending up in the whole live aquaculture product - this is just basic spread sheet math. These numbers do not mean that 70-80% of feed not deposited in aquaculture organism is waste, because some species-specific percentage goes into metabolic energy, but the remaining feed products go into gas (CO2 and nitrogen), liquids, dissolved solids and particulate wastes.

Processing losses and potential offal recovery/conversion have to be considered in RAS aquaculture production facility design to realize full RAS concept economic/profit potential. At BCI we have been examining the economics and required technologies to convert those wastes into cost offsets and higher RAS profits. We call our process Integrated Species Recirculating Aquaculture Systems (ISRAS). We have focused on techniques that allow the ISRAS concept to convert typical RAS wastes (feed particulates, dissolved nutrients, and energy) into highest value products possible. With offal, the conversion process can be through digestion and re-introduction into the ISRAS system at one of the lower trophic levels as feed particulates or algal fertilizers - assuming optimized production economics and onsite processing.

The Integrated Species Recirculating Aquaculture System (ISRAS) concept that BCI is developing is more than a typical multi-trophic poly-culture system, it is  a strategic business process technology and the only RAS specifically designed to accomplish the most economically sensitive production task next to the primary product itself - recovery of aquaculture waste nutrients and energy. While RAS systems are generally and currently thought to be more expensive than traditional aquaculture production methods - continued increasing of aquaculture feed costs will make the ISRAS waste feed recapture process the consistently lowest cost aquaculture production technology of the near future.

Durwood M. Dugger

120304

(re-edited from original comment on 101024.)