INTRODUCTION

Microalgae have the potential to meet the growing energy demand expected in the coming decades. These organisms have many advantages over traditional terrestrial crops in biofuel production. Among these advantages, it is the ability to produce biomass per area and time unit, representing a large productivity beyond the obtained by the main land cultures, used as f eed stock for production of other derivatives. Another feature in favor of microalgae is that they do not require fertile land and clean water, because they can be produced at marginal areas without competing with food production. However, there is no common consensus in the short term, on the economic viability of other products production from these organisms (De Azeredo, 2012).

Microalgae have been the subject of studies for multiple purposes, especially by the United States and Brazil, through research programs that began in the 70’ s, but which are gaining prominence only now . These unicellular organisms inhabital most all existing environments. However, in most cases, the microalgae live in marine environments.

Currently, there are studies for an efficiently production from biomass, in particular the microalgae, destined to food, energy and biofuels. Many centers in Spain, USA, Cuba, Brazil, Japan, China; etc. develop research in order to produce various microalgae products with high added value.

The production of microalgae has benefits that can be summarized in three areas: economic, environmental and social.

Economic - their biomass is renewable, which will allow greater diversification. The raw material of interest and by-prod ucts generated f rom th eir processes can have other uses (insecticides, fertilizers, animal feed, etc.), according to economic viability. With this, we can develop agribusiness, reduce imports and generate new exportable products.

Environmental - the production and use of biomass can contribute to the regeneration of soils unsuitable for agriculture, increase biodiversity and reduce global warming through carbon sequestration. Currently the production of fuels f rom biomass, includ ing biodiesel and bioethanol, are growing in the world, due to the need to find a viable solution to produce sustainably energy. The microalgae biomass meets this demand.

Social – it has a positive social impactas it creates jobs, improving the quality of life from this people.

Increased know ledge about the importance of protecting the environment from the potential impacts associated with manufacturing and/or consumed products, has increased the interest in developing methods to understand and manage better these impacts. One method developed for this purpose is the life cycle anal sis (LCA). The life cycle includes taking all phases of the existence of a product or service, including extraction, production, distribution, use and disposal. This cycle can be understood by the term “from cradle to grave” .

The evaluation of the life cycle is a technique for determining the aspects and potential environmental impacts associated with a product. It consists in compiling an inventory of relevant inputs and outputs of the systems, evaluating the potential environmental impacts associated with them, and to interpret results and objectives of the study (ISO Standard, 2006a, 2006b).

LCA is a methodological tool to analyze quantitatively the CV of products / activities within the context of its environmental impact. The application of this tool has undergone major changes during the nineties. It was quickly incorporated at the high eststrategic levels Joint Research Center y European Commission ( 2010), includingin decision-making and corporate policy levels. LCA is currently used to evaluate a wide range of products and activities, from design to finished product, also in energy systems, food production and transportation alternatives.

In add ition, research conducted by universities, institutes and consulting firms have further developed the procedures and methods to carry out the LCA. It was declared by the Joint Research Center y European Commission, (2010), that the scope of an LCA depends on the objective to beachieved, so this methodology is still under development. This constant development clearly shows that there is no universal method applicable in all situations.

This study aims to evaluate the environmental impact of the production of microalgae biomass on a large scale, by evaluating its life cycle (LCA) in order to obtain compounds with high added value, for example, carotenoids.

METHODS

The current literature (Goedkoop et al., 2009), considers the impact categories associated with medium and final levels. These 19 types of medium level impact are shown in Table 1.

Table 1

Categories of Environmental Impacts Associated with Medium Level, Their Indicators and Measures (Goedkoop et al., 2009)

In turn, these 19 impact categories were pooled and transformed into 4 final level of impact categories (Table 2).

Table 2

Categories of Impact to Medium and Final Levels (Goedkoop et al., 2009)

• Damage to human health (HH): the life-cycle assessments seek commonly to infer the damage of a production process to human health, using the concept of disability -adjusted life years (DALY). The values for DALY have been reported for a wide range of diseases (Goedkoop et al., 2009)

• Damage to environmental biodiversity (EB): ecosystems are heterogeneous and complex to monitor. Various treaties, decrees and informal agreements (UNCED, PNUMA, the European Council) have included a list of attributes that are important to humanity such as biodiversity, esthetic and cultural values, ecological functions and services, ecological resources and functional information (genetic material) (Goedkoop et al., 2009).

• Damage to the availability of resources (AR): it considers the risk to which humanity will be exposed due to the lack of resources for future generations. Resources depletion is the only problem that must be monitored permanently Goedkoop et al. ( 2009).

• Damage to the artificial environment (AE): this impact category considers the damage to the quality of life, causing pandemics and disasters to human heritage (Goedkoop et al., 2009).

• To apply the methodology of LCA, we should consider four phases (Goedkoop et al., 2009):

  1. Phase 1.- Determining the objectives and scope of the study The scope and level of detail of an LCA depends on the subject matter and its utility use. The depth and bread th of LCA can differ considerably depending on the specific purpose for which it is intended.

  2. Phase 2.- Inventory analysis It is an inventory of the input and output of the studied system and involves the relationship among the data necessary to respond to the defined goal.

  3. Phase 3.- Impact assessment The objective of this phase is to provide additional information to help assessing the previous stage and understand better their environmental significance.

  4. Phase 4.- Interpretation The interpretation of the LC occurs in the final phase of the LCA process, where results are summarized and discussed as a basis for conclusions, recommendations and decisions in accordance with the purpose and scope.

RESULTS AND DISCUSSION

Qualitative Assessment of the Potential Environmental Impact of Microalgae Biomass

Table 3 shows the results of the qualitative assessment of the impact of microalgae LC. These data were obtained from the literature review (Shelef et al., 1984; Sawayama et al., 1995; Richmond, 2004; Rodríguez et al., 2009, 2015; Widjaja et al., 2009; Collet et al., 2011; Benjamin, 2013) and the consultation with mechanical engineers, chemists and biologists, as well as by working skills of an expert’s team (Delphi technique, Kendall w).

Table 3

Results of the Qualitative Assessment of the Potential Environmental Impact of Microalgae Biomass. (+) Positive Impact, (-) Negative Impact, (0) No Impact.

From the above table it can be concluded:

• Positive impact: 53.57%

• No impact 39.29%

• -Negative impact 7.14%

Observing the results obtained, the microalgae are viable for economic activities and the negative impacts to the environment are very low.

Life Cycle Assessment of the Microalgae Production

In Figure 1 the life cycle of microalgae for the purpose of obtaining carotenoids, their stages (6) and activities (20) are shown.

Figure 1
Stages and A ctivities of the Microalgae Life Cycle (Own Origination)

1. Phase 1: Determining the purpose and scope of the LCA. Objective: To determine qualitatively the environmental impact of microalgae.

2. Scope: production of carotenoids from the microalgae.

3. Phase 2: Analysis of inventory.

   Two data inventories were made: - The inventory of impact categories at the medium and final levels, presented in Table 1.

4. - The inventory of LC microalgae activities and the list of activities that are part of LC, that are presented in Table 4.

Table 4

Life Cycle of Microalgae Aimed at Carotenoids Production

1. Phase 3: Impact assessment.

   The Environmental Impact Weighting Matrix (20 * 19 * 4 base) is used, which assesses the impact of the 20 activities of microalgae LC in 19 environmental categories and their consequences for the environment [5]. To conduct the evaluation, each activity is analyzed in each environmental category , evaluating the impact magnitude according to the recommendations in Table 5. The applied classification is an own proposal of the authors.

Table 5

Scale for impact assessment (Own origination)

The evaluation of each pair of activities (environmental category) can be seen in Table 6. The identification of each activity can be found in Table 4. The value assigned to each activity pair of environmental category is the result of a work executed with the group technique (Delphi-Kendall) with the participation of experts (mechanics, engineers, chemists and biologists).

Table 6

Primary Data for the Environmental Impact Weighting Matrix

1. Phase 4: Interpretation. Knowing the environmental effects values for each activity, it is possible to calculate the average of the impact which has effect on the environment by:

   • Absolute value of the activity (i): i =Σ (environmental impact j) / 19 (1) where i =1…20; j=1…19.

   • Relative value of the activity i ( % ): % = absolute activity impact i/ 3∙100 (2)

   • Specific weight of the activity i (%): i% =relative value of the activity / 20 (3)

   • Sum k (%) = Σ actual specific activities belonging to k (4) where k = 1...6, corresponding to the number of stages of microalgae LC (Table 4).

Table 7. Shows the impact values for each of the activities listed in Table 4.

Table 7

Activities Impact Values

The total impact on the ecosystem is 4.47

Furthermore, it is possible to calculate from Table 5, the environmental impact by the medium level impact categories. The weighting of these effects is calculated as:

• Relative value of the environmental impact j (%) =Σ (activity i) /20 /3∙100 ( 5)

where

j = 1…19; i = 1…20

Figure 2 presents the results from the environmental impact analysis in accordance with each of the indicators th at characterize the categories of impact in medium level.

Figure 2
Weighting of the Environmental Impact by Medium Level Categories.

As can be seen, the greatest impact corresponds to the exhaustion of fossil resources with a value of 1.14%. As it can be seen, the greatest impact corresponds to the exhaustion of fossil resources with a value of 1.14%. Other categories with lower results than the latter are: human toxicity and depletion of water with 0.61% and 0.53%, respectively. There are 9 categories that have no impact, in which the value of the indicator is 0.

Figure 3 shows the magnitude of the environmental impact in the four final level categories.

Figure 3
Effect Evaluation in Accordance with the Impact (%)

The sum of these four variables is the total impact equivalent to 4.47%. There is not damage to the artificial environment. The data presented in Table 8 are a proposal of the authors.

Table 8

Effect Evaluation in Accordance with the Impact (%)

Considering Table 8, that shows the weighted value in relation to the impact (%), it was found that microalgae biomass can be considered as a low impact activity. In previous work, Rodríguez et al. (2009, 2015), used the impact matrix for the analysis of the biomasses from sugarcane and Jatropha curcas (Pinion–meek ) impact. Table 9 shows that comparison.

Table 9

Comparison of the Weighted Environmental Impact of Biomass LC

CONCLUSIONS

• By using the weighting matrix, it is possible to determine the weighted magnitude of the impact. With this information, it is possible to know the environmental impact of each activity of the LC and make decisions to reduce it.

• The weighted environmental impact of microalgae production is 4.47%, which is classified as small impact and shows that the biomass is environmentally sustainable. That points this biomass as a source of domestic production, and competitiveness with other final products.

• The production of carotenoids from microalgae is actually sustainable from an environmental point of view. However, a deeper analysis of the life cycle and through out the supply chain is necessary. Due to the increasing number of issues related to global climate change, an assessment of the potential of microalgae to mitigate emissions of greenhouse gases, especially CO2, would be important.

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Notes