Life cycle assessment of heterotrophic algae omega-3

Alleen voor leden beschikbaar, wordt daarom gratis lid!

Overig advies 28/11/2021 11:46
Highlights
•Comprehensive life cycle assessment of commercial algae omega-3 DHA (docosahexaenoic acid) assessing 6 impact categories

•Omega-3 DHA from algae has 30–40% lower impact on climate change than fish oil.

•Sugarcane cultivation has the largest contribution for most impact categories.

•Most sensitive parameters are sugar to omega-3 conversion yield and sugarcane yield.

•The allocation choices do not significantly affect the overall impacts.

Abstract
Fish oil has traditionally been the primary source of long chain omega-3 fatty acids, which are essential nutrients for human diets as well as many aquaculture and animal feeds. The demand for fish oil is growing rapidly, due to an expanding aquaculture sector as well as rising demand in pet and livestock feeds, while the availability of fish oil from wild caught fish has leveled off over the past decade. Fish oil is not easily replaced and alternative sources are required to meet the growing global demand. One of the most promising alternatives is microalgae - the original source of long chain omega-3s. To understand the environmental impacts of omega-3s produced by heterotrophic algae, a comprehensive Life Cycle Assessment (LCA), assessing six impact categories, was conducted for two algae omega-3 DHA (docosahexaenoic acid) products, in powder and liquid suspension formats. These products are manufactured at industrial scale using sugarcane for both feedstock and a renewable energy source. The life cycle impact assessment results for algae omega-3 DHA indicate that sugarcane cultivation has the largest contribution for most of the categories. A sensitivity analysis revealed that the sugarcane yield, and the sugar to omega-3 DHA yield, were the most relevant parameters, and that the choice of allocation methodology did not have a strong influence on the results. A comparison with fish oil, using data publicly available in LCA databases, indicated that the two formats of the commercial algae omega-3 DHA product offer about 30–40% lower impact on climate change than fish oil.

Previous article in issueNext article in issue
Keywords
Omega-3FeedLife cycle assessment (LCA)Fish oilSugarcaneAlgae
1. Introduction
Long chain omega-3 fatty acids—eicosapentaenoic (EPA) and docosahexaenoic (DHA) acids—are essential for human diets as well as many aquaculture and animal feeds. The developmental and health benefits of long chain omega-3s for brain, eye and heart health for humans is well documented [1]. Many of these same benefits are important for animal development and growth as well.

Fish oil has traditionally been the primary source of long chain omega-3s, but is sourced from finite marine fisheries, and supply has leveled off at around 1.1 million tons in recent years [2]. A recent study tracked flows of long chain omega-3 stocks through global production, supply and utilization pathways and found a significant gap in supply [3]. This supply gap will continue to widen as demand rises, especially from the aquaculture sector which consumes approximately 75% of the available crude fish oil [4]. Aquaculture is one of the fastest growing food systems in the world, with fed species representing nearly 70% of global aquaculture production [5]. Aquafeed, especially for carnivorous species, historically relied on forage fish for fish meal and fish oil, to provide the required nutrients such as protein and omega-3 fatty acids. With the global supply of forage fish at a plateau, there has been rising demand to limit the use of wild marine fish in aquaculture feed in order to reduce pressure on already stressed wild fisheries [6]. A recent study of salmon feed in Norway showed that over 70% of aquafeed is now sourced from plant origins [7]. For example, fish meal was the original source of protein in aquafeed and now is partially being replaced by soy protein [7]. Novel ingredients such as insect meal and protein derived from single cell bacteria are emerging as alternative protein sources to fish meal and soy [8].

In an effort to reduce the use of fish oil in aquafeed, some fish oil has been replaced by rapeseed or camelina oil which meets the energetic needs of farmed fish, but not the omega-3 needs [7]. Dropping levels of long chain omega-3s in carnivorous fish, especially salmon, can impact fish health and welfare [9]. In addition, the change in nutritional quality of salmon, an increasingly popular species in the global market, can impact public health due to less intake of long chain omega-3s [10].

Fish oil contains key long chain omega-3 polyunsaturated fatty acids (PUFAs), eicosapentaenoic acid and docosahexaenoic which are not easily replaced. Therefore, alternative sources are required to meet the growing demands, not only of aquaculture, but also livestock production and direct human consumption [11]. Thus, scientists have looked to the original source of long chain omega-3 PUFAs – microalgae –as a potential solution.

Heterotrophic microalgae from genera such as Schizochytrium, Ulkenia, and Crypthecodinium produce algae products that are rich in DHA [12]. Algae from these genera have been selected based on their ability to produce large quantities of DHA from a carbon feedstock, through conventional fermentation.

Corbion has developed and commercializes omega-3 DHA products which utilize an algae of the Schizochytrium genus to produce biomass that is rich in DHA and is applied as an alternative to fish oil in feed for aquaculture and livestock, as well as pet food. This heterotrophic microalgae product is manufactured via fermentation in Orindiúva, Brazil, using sugar from sugarcane as feedstock. The production site is co-located with a sugar mill enabling the efficient use of energy from sugarcane by-products. This novel omega-3 DHA source shows promise for reducing the amount of wild fish needed in feed for farmed fish and livestock, as well as pet food, while maintaining or improving animal health.

A comprehensive understanding of the environmental impacts of algae feed ingredients is lacking [8]. Although algae-based ingredients reduce the demand of wild fish, other environmental impacts associated with the production of these algae ingredients must be evaluated. The potential environmental trade-offs need to be well understood to ensure the sustainability of algae-based omega-3 production. Life cycle assessment (LCA) is a well-established methodology that uses a holistic approach to identify trade-offs between environmental impacts to avoid shifting burdens over the value chain. Due to characteristics such as fast growth, high cell density, and high oil productivity, heterotrophic algae systems are of increasing interest [13], however, to our knowledge, there are no LCAs available in the public domain about commercialized heterotrophic algae systems [[13], [14], [15]]. The literature studies on the LCA of heterotopic algae systems focus on biodiesel production. Other LCA's on feed and food production of protein and oil ingredients are based on lab or pilot data [[14], [15], [16]].

This paper aims at providing cradle-to-gate LCA information on commercially produced omega-3 DHA from heterotrophically grown microalgae to scientists, feed producers, and aquaculture and animal farmers, who seek to understand the environmental sustainability aspects of heterogeneous algae products. The novelty of this LCA study is the use of industrial data for algae omega-3 production. Additionally, the LCA results are compared with the environmental impact of producing omega-3s from fish oil. The commercial production of omega-3 DHA via heterotrophic microalgae has optimization potential that can be realized through continuous product and process development. In this study, the impact of some of these improvements are quantified to provide an outlook of the potential of algae-based products.

2. Materials and methods
This LCA was performed according to the standard methodology described in ISO 14040 series by the International Organization of Standardization [17,18]. The LCA model was created in SimaPro developer software version 9.1 (PRé Sustainability, The Netherlands).

2.1. Goal and scope definition
The goal of this LCA is to quantify the environmental footprint of omega-3 DHA produced from heterotrophically grown microalgae, commercialized under the name of AlgaPrime™ DHA. The results are intended to be used as input in the LCA of feed formulations and to understand the environmental sustainability of the fish oil alternative for omega-3s. The study relied on an attributional LCA approach, therefore the potential impact of feed and food system transformation due to heterotrophic microalgae production was not considered.

The functional unit was defined as 1 kg omega-3 fatty acids. Although other components of the algae biomass, such as proteins, carbohydrates, and other fatty acids, have nutritional value for feed, omega-3s are the reason for inclusion of the algae product in feed. For this reason, the choice of the functional unit reflects the primary function of the algae omega-3 DHA product. Furthermore, this functional unit allows comparison between the algae omega-3 products and fish oil. In the case of the algae product studied, DHA is the only long chain omega-3 fatty acid, whereas in the case of fish oil, both EPA and DHA are present. Traditionally, aquafeed contains varying ratios of EPA and DHA depending on the type and amount of fish oil included. In a study conducted on salmon, it was shown that omega-3s are essential to the growth and health of the fish and when omega-3s were excluded from the diet entirely, the fish growth rate was slower and overall health of the fish decreased [9]. DHA appears to be the more essential of the two PUFAs and has been suggested that the long chain PUFA requirement of healthy salmon can be met by DHA alone [19]. Consistent with previous research, a recent study found that DHA has higher omega-3 retention in the filet of salmon versus EPA, which is typically metabolized by the fish [20]. In additional studies by Nofima, one of the leading aquaculture research institutes in Norway, it was determined that DHA rich Schizochytrium microalgae effectively replaces fish oil in diets of Atlantic salmon in both freshwater and sea-water life stages [21].

The omega-3 DHA algae is produced in two feed ingredient formats - powder and liquid suspension - to offer flexibility for feed producers. A diversity of feed formulation formats is needed for aquaculture species, livestock, and pets due to consumption patterns, digestive and absorption dynamics, and operational application needs. Both formats are included in the scope of this study:
1)
Powder or biomass - Oil high in omega-3 DHA is encapsulated within the algae cell to form a free-flowing dry powder.

2)
Liquid suspension – Blend of omega-3 DHA-rich algae and vegetable oil.


Hereafter, we will refer to these products as “algae omega-3 DHA powder” and “algae omega-3 DHA liquid suspension”. Both products have a similar DHA content of 28–30 wt%.

The scope of this LCA is cradle-to-gate and includes (1) sugarcane cultivation and harvest, (2) processing sugarcane to sugar (with energy and ethanol as co-products) and (3) conversion of sugar into algae omega-3 DHA by Corbion. The production of the algae omega-3 DHA products is located at a Corbion facility in Brazil where current production is ongoing. The input data for production used in this study is based on calculations for full scale production, using techno-economic models and manufacturing production data from 2019. Manufacturing of production equipment, buildings, and other capital goods on the manufacturing site of Corbion are not included in the scope. Due to the long lifetime of the plant, the contributions are expected to be small.

2.2. Environmental impact categories
The characterization method used was the EF (Environmental footprint) 3.0 impact assessment method [20] adapted to SimaPro 9.1. This is the impact method published for use during transition phase of the Environmental Footprint initiative [22]. The study covers the six most relevant impact categories defined by the product environmental footprint guidelines category rules (PEFCR) for animal feed [23]: (1) Climate change (GWP100a based on the Intergovernmental Panel on Climate Change - IPCC, 2013 [24]), (2) Particulate matter (impact on human health [25]), (3) Acidification of terrestrial and freshwater (Accumulated Exceedance [26]), (4) Land Use - LANCA model [27], (5) Terrestrial Eutrophication (Accumulated Exceedance [26]) and (6) Water use - AWARE model [25].

2.2.1. Biogenic carbon
Sugar used for algae omega-3 DHA production contains biogenic carbon which is stored in the plant tissue during plant growth and converted to omega-3 DHA. In this LCA, biogenic carbon does not earn a credit for carbon uptake because most of the carbon will eventually be released again as CO2 or CH4 after animal or human consumption in less than a few years. This means that the carbon uptake of the crop during cultivation is not considered and neither are the CO2 emissions after consumption. This approach is consistent with the PEF (Product environmental footprint) guidelines [28].

2.2.2. Additional information
As additional information, the water scarcity risk was assessed using a water risk assessment tool - Aqueduct Water Risk atlas [29].

3. Process description and life cycle inventory
The production of algae omega-3 DHA has five main steps: (1) cultivation of sugarcane and transportation to sugar mill, (2) processing of sugarcane into multiple products: sugar, ethanol, and electricity, (3) transformation of sugar by algae into DHA via fermentation and (4) downstream processing of algae into the final products. The production system can be seen in Fig. 1. Below is a detailed description of each step.

see & read more on
https://www.sciencedirect.com/science/article/pii/S2211926421003131



Beperkte weergave !
Leden hebben toegang tot meer informatie! Omdat u nog geen lid bent of niet staat ingelogd, ziet u nu een beperktere pagina. Wordt daarom GRATIS Lid of login met uw wachtwoord


Copyrights © 2000 by XEA.nl all rights reserved
Niets mag zonder toestemming van de redactie worden gekopieerd, linken naar deze pagina is wel toegestaan.


Copyrights © DEBELEGGERSADVISEUR.NL