Le alghe e l’agricoltura: politica statunitense per la produzione di biomasse algali

The place of algae in agriculture: policies for algal biomass production

Emily M. Trentacoste , Alice M. Martinez2 and Tim Zenk2, 3

(1)Scripps Institution of Oceanography, University of California-San Diego, 9500 Gilman Dr., La Jolla, CA 92093, USA

(2)Sapphire Energy, Inc., 3115 Merryfield Row, San Diego, CA 92121, USA

(3)Algae Biomass Organization, 125 St. Paul Street, Preston, MN 55965, USA

Emily M. Trentacoste – Email: etrentac@ucsd.edu Published online: 6 March 2014

Abstract
Algae have been used for food and nutraceuticals for thousands of years, and the large-scale cultivation of algae, or algaculture, has existed for over half a century. More recently algae have been identified and developed as renewable fuel sources, and the cultivation of algal biomass for various products is transitioning to commercial-scale systems. It is crucial during this period that institutional frameworks (i.e., policies) support and promote development and commercialization and anticipate and stimulate the evolution of the algal biomass industry as a source of renewable fuels, high value protein and carbohydrates and low-cost drugs. Large-scale cultivation of algae merges the fundamental aspects of traditional agricultural farming and aquaculture. Despite this overlap, algaculture has not yet been afforded a position within agriculture or the benefits associated with it. Various federal and state agricultural support and assistance programs are currently appropriated for crops, but their extension to algal biomass is uncertain. These programs are essential for nascent industries to encourage investment, build infrastructure, disseminate technical experience and information, and create markets. This review describes the potential agricultural policies and programs that could support algal biomass cultivation, and the barriers to the expansion of these programs to algae.

Introduction

Algae are simple, photosynthetic, generally aquatic organisms that, like plants, use energy from sunlight to sequester carbon dioxide (CO2) from the atmosphere into biomass through photosynthesis. Plants evolved from ancient algae ancestors, and the photosynthetic machinery in both plants and algae originally came from the same source: cyanobacteria (Falcón et al. 2010; Fehling et al. 2007). Although algae and plants differ in many ways, the fundamental processes, such as photosynthesis, that make them so distinguished among Earth’s organisms and valuable as crops, are the same.
Certain strains of algae have been used for anthropogenic purposes for thousands of years, including as supplements and nutraceuticals (Kiple and Ornelas 2000) and in the fertilization of rice paddies (Tung and Shen 1985). As early as the 1940s, other strains were identified as possible fuel sources (Borowitzka 2013a) because of their ability to produce fuel or fuel precursor molecules. Large-scale production and cultivation systems, including photobioreactors and outdoor open ponds, were developed in the early 1950s in the U.S., Germany, Japan, and the Netherlands (Borowitzka 2013b; Tamiya 1957). By the onset of the U.S. Department of Energy’s (DOE) aquatic species program (ASP) in the U.S. in 1980, various species of microalgae and cyanobacteria were being produced and farmed on commercial scales around the world, and had been for over 20 years, mostly for the health food and nutritional supplement industries (Borowitzka 2013b).
Microalgae have evolved to be practically ubiquitous throughout the globe, and their varied distributions and evolutionary histories (Fehling et al. 2007) are reflected in extremely diverse metabolic capabilities between species (Andersen 2013). These diverse metabolisms produce a myriad of compounds with anthropogenic relevance including nutraceuticals, such as the carotenoids produced by Dunaliella and Haematococcus (Borowitzka 2013a, b), the polyunsaturated fatty acids (PUFAs) produced by various species (Ratledge 2004), and the high-value proteins and carbohydrates available in whole-cell supplements of Spirulina and Chlorella (Görs et al. 2010; Khan et al. 2005). Some microalgae produce compounds of biotechnological interest including fluorescent compounds, such as phycoerythrin, and many produce isoprenoid molecules that can be used in food and over-the-counter products (Andersen 2013).

Microalgae have also been identified as attractive sources of biofuel because different species can produce a variety of fuel products. Various microalgal species have the ability to produce large quantities of lipid while sequestering CO2, particularly neutral lipids in the form of triacylglycerol (TAG), which can be converted to fatty acid methyl esters (FAMEs), the main components of biodiesel (Hossain et al. 2008), through trans-esterification, or refined into other fuel constituents (Pienkos and Darzins 2009). Total lipids and other biomass constituents can be converted into crude oil alternatives through thermochemical processes such as hydrothermal liquefaction (Barreiro et al. 2013). Microalgal carbohydrates can be fermented into ethanol, and some species can produce biohydrogen (Radakovits et al. 2010). In addition to their diversity of products, microalgae are attractive as fuel sources because many species grow relatively fast compared to terrestrial plants and can be grown on brackish or saline water, thus avoiding the use of unsustainable quantities of freshwater, an increasingly limited resource (Dismukes et al. 2008). Table 1 provides an overview of some commercial algal products and potential sources.

Table 1

Commercial products from algae
Product
Use
Example source
Reference
β-Carotene
Supplement
Dunaliella
Lamers et al. (2008)
Astaxanthin
Supplement
Haematococcus
Lorenz and Cysewski (2000)
Whole-cell nutraceuticals
Supplement
Spirulina
Khan et al. (2005)
Chlorella
Görs et al. (2010)
Aquaculture feed
Animal feed
Tetraselmis
Gladue and Maxey (1994)
Isochrysis
Gladue and Maxey (1994)
Polyunsaturated fatty
Supplement
Crypthecodinium
Jiang et al. (1999)
acids (PUFAs)
Shizochytrium
Spolaore et al. (2006)
Phycoerythrin
Biotechnology
Red algae
Pulz and Gross (2004)
Fuel molecules
Energy
Botryococcus
Ashokkumar and Rengasamy (2012)
Scenedesmus
Mandal and Mallick (2009)
Neochloris
Gouveia et al. (2009)
Anticancer drugs
Pharmacueticals
Symploca
Coates et al. (2013)

Algaculture, or the farming of algae (Savage 2011), merges the requirements of traditional terrestrial plant agriculture such as sunlight, water, CO2, nutrient inputs, and harvesting systems with additional aquaculture requirements such as self-contained aquatic systems, water quality, and waste disposal/recycling (Fig. 1). Because of their capability to produce commodities that span multiple markets, including those of health food, nutraceuticals, pharmaceuticals, animal feed, chemicals and energy, algae are uniquely versatile crops (Rosenberg et al. 2008). These diverse metabolic capabilities are due, in part, to the diversity of strains found within the algal lineage. Algae strains grown for food purposes, such as Spirulina, have a starkly different metabolic profile from strains grown for energy, such as Scenedesmus. The diversity of their end products, and their cultivation using both agriculture and aquaculture practices make algae unique among other agricultural products.

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Fig. 1

Algaculture in the U.S. Algaculture can take place in closed photobioreactors, like those of Algenol in Florida (a) and Solix Biosystems in Colorado (b), or in open ponds like those of Sapphire Energy, Inc. in New Mexico (c). Like agriculture, algae cultivation requires growth as well as harvesting infrastructure, such as that of Sapphire Energy Inc. (d)
Despite significant overlap with both traditional agriculture and aquaculture (which Congress has defined as agriculture, including that of aquatic plants) (Food and Agriculture Act of 1977, 1977), algaculture has not yet been afforded an official position within Title 7 of the U.S. Code (USC) for Agriculture. There are currently a number of other crops that share commonalities with algae in their cultivation practices or diversity of end-use markets, but these have all been designated a place within Title 7. For example, the commercial cultivation of aquatic plants, such as seagrass, is eligible for a diverse array of agricultural programs. Similarly, the farming of terrestrial crops for renewable energy, which shares the same end market and purpose as many algal-farming operations, benefits from its definition as agriculture.

Funding for research and development of algal biomass cultivation has increased over the last decade, and has led to the emergence of research programs, private projects, demonstration- and commercial-scale facilities across the U.S. (Fig. 2). The increase is primarily due to the growth of the algal biofuel industry in response to the demand for alternative fuel sources driven by the renewable fuel standards (RFS) (Tyner 2013). While the use of algae as functional food or feed ingredients is also on the rise (Ibañez and Cifuentes 2013), there are currently few federal program resources focused in this area. The production of algae for any end product is a two-phase process involving the farming and cultivation of algal biomass followed by processing of the harvested biomass. The ability of the algal biomass industry to access federal programs that support the agricultural phase is imperative for future growth. This report analyzes the place of algae in the current agricultural policy and funding landscape, and the opportunities and pitfalls that exist for algae within this policy framework.

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Fig. 2 Algae projects in the U.S. Algal biomass projects exist in almost every state in the U.S. Blue pins denote a research institution, green denote a private project or company

read more on: http://link.springer.com/article/10.1007/s11120-014-9985-8/fulltext.html

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