Energy production from microalgae biomass: carbon footprint and energy balance

Abstract

Bioenergy sources are promising alternatives for energy production in a sustainable world. Nevertheless many research and detailed analysis are necessary to measure in which circumstances they can contribute to it. This paper focuses on microalgae biomass combustion to produce heat and compares the use of different electricity sources with respect to Greenhouse Gas (GHG) emissions and Net Energy Ratio (NER). Some fossil sources were used as reference. The methodology was based on ISO 14040/44 standards and most of the data were obtained from scientific publications. The results showed that NER from microalgae combustion is still disadvantageous compared to fossil options. Microalgae GHG emissions were higher than fossil using the United States electricity grid but lower using the Brazilian one. Regardless of the fossil options show slightly better yields related to microalgae in the two categories analyzed, the fossil energy technology is mature and has less space for improvements while microalgae is in its infancy and have many technological solutions being developed.

Toxicity alleviation for microalgae cultivation by cationic starch addition and ammonia stripping and study on the cost assessment

“…In addition, the different parameters of facilities used by two studies also caused the difference of cost. 48,49 Since 700 L raw AD-SM yielded 11 200 L AD-SM at 16-fold dilution, it was necessary to treat the AD-SM in 8 batches. However, it only took 2 batches to treat the AD-SM with 4-fold dilution.…”

Nutrients from anaerobic digestion effluents for cultivation of the microalga Nannochloropsis sp. — Impact on growth, biochemical composition and the potential for cost and environmental impact savings

“…These energy demands could significantly impact the energy return on investment of bioenergy production from microalgae. When considering the overall energy of biodiesel production (including cultivation and processing), nutrients have previously been found to account for as much as 14-61% of the total energy demand [5,77,[79][80][81]. In this case, the use of ADE decreases nutrient input energy demand to less than 0.8% and 2.5% of the energy content of the biomass and biodiesel, respectively.…”

Evaluating microalgae‐to‐energy ‐systems: different approaches to life cycle assessment (LCA) studies

“…As the production of third generation microalgae‐based energy is increasing being cited as a climate change solution, it is not unexpected that GWP was the dominant environmental impact factor measured in the majority of the LCAs selected, appearing in 17 of 18 studies. The GWP is representative of the emissions of several greenhouse gasses (primarily CO 2 , N 2 O, CH 4 ).…”

“…While both fresh and salt water can theoretically be used, fresh water represents fewer issues in terms of operational costs, because salt must be extracted from sea water via an evaporation phase and then disposed of . In addition, sunlight potential and temperature of the location have been shown to directly influence the growth rate of the algae . The need for both heat and a high proportion of sunny days governs the potential land requirements for outdoor algae production .…”

“…Biomass for energy, and particularly liquid biofuels for use in transport, have been of increasing interest to policymakers seeking to shift toward more sustainable economies. The development of green fuel technologies with minimal carbon emissions is one option that can help meet global energy requirements in a more sustainable fashion, reducing society's over‐reliance on fossil fuels, which currently meet 80% of the world's energy demand …”