Distribution of Heavy Metals from Flue Gas in Algal Bioreactor

Algae are microscopic organisms with a great potential to produce biomass and lipids at productivities several times higher than terrestrial crops. To grow, these organisms consume carbon dioxide (CO2), a greenhouse gas. This gas, emitted primarily by power plants after coal burning, can be effectively used for algae production, thus resulting in CO2 remediation and biomass beneficial utilization as feedstuff, industrial filler and biodiesel feedstock. However, since coal is a fuel mined from the earth’s crust, it contains heavy metals that are released during coal burning and inevitably enter the algal cultivation system, contaminating the water were algae is grown, the algal biomass and the products derived from such biomass. The distribution of heavy metals from flue gas in algal cultivation systems is unknown, yet necessary to advance this industry. This study focused on quantifying the distribution and effects that ten coal-derived heavy metals (Cu, Co, Zn, Pb, As, Se, Cr, Hg, Ni and Cd) will have on algae strain Scenedesmus obliquus and on the potential products derived from this algae

Quantitative Assessment of Microalgae Biomass and Lipid Stability Post-Cultivation

Processing of microalgal biomass to biofuels and other products requires the removal of the culture from a well-controlled growth system to a containment or preprocessing step at non-ideal growth conditions, such as darkness, minimal gas exchange, and fluctuating temperatures. The conditions and the length of time between harvest and processing will impact microalgal metabolism resulting in biomass and lipid degradation. This study experimentally investigates the impact of time and temperature on Nannochloropsis salina harvested from outdoor plate photobioreactors. The impact of three temperatures, 4°, 40° or 70°C, on biomass and lipid content (as fatty acid methyl esters) of the harvested microalgae was evaluated over a 156 hour time period. Results show that for N. salina, time and temperature are key factors that negatively impact biomass and lipid yields. The temperature of 70°C resulted in the highest degradation with the overall biofuel potential reduced by 30% over 156 hours. Short time periods, 24 hours, and low temperatures are shown to have little effect on the harvested biomass

Influence of heavy metals from flue gas integration with algal production on biodiesel production

Large-scale microalgae production is expected to be integrated with point source carbon dioxide sources such as coal-fired power plants for carbon supply and environmental benefits. Although industrial flue-gasses pass through purification systems, submicron-size particles enriched with heavy metals are emitted to the atmosphere and eventually reach the ground resulting in increased health issues. Algae production integrated with flue-gas will ultimately have heavy metals introduced into the growth media which can be absorbed by the microalgae and potentially degrade growth and contaminate the biomass. This study experimentally evaluates the distribution and impact of heavy metals present in flue-gas on microalgae production systems. Two different microalgae species were evaluated, Scenedesmus and Nannochloropsis, cultivated in batch reactors with media containing at a minimum of ten heavy metals (Cu, Co, Zn, Pb, As, Se, Cr, Hg, Ni and Cd) at concentration representative of flue-gas integration. Heavy metal impact was quantified through biomass growth, lipid content, and heavy metal analysis through inductively coupled plasma mass spectrometry and atomic absorption spectrometry. The results show that heavy metals positively impacted Scenedesmus grown at the reference concentration while negatively impacted Nannochloropsis growth. Further study focused on Scenedesmus showed that heavy metals accumulated mainly in biomass and very low concentrations were measured in the media. Environmental impact assessments show most heavy metals in the effluent water complied with the recommendations for irrigation water and drinking water standards established by the Food and Agricultural Organization of the United Nations and the U.S. Environmental Protection Agency respectively showing microalgae were effective in removing metals from the growth media. This research shows that bioremediation of carbon dioxide and heavy metals in combination with energy production can be integrated and beneficial. Further work is dedicated towards understanding the end fate of heavy metals in terms of end products such as biofuel and algae meal

USCID fifth international conference

Presented at the fifth international conference on irrigation and drainage, Irrigation and drainage for food, energy and the environment on November 3-6, 2009 in Salt Lake City, Utah.Includes bibliographical references.The Logan and the Blacksmith Fork irrigation systems in the Cache Valley, Utah, convey water distribution through earthen canals. Previous researchers and local water masters reported the existence of seepage problems in these canals, but there is very little knowledge of the amount of seepage, and of the spatial locations and temporal variation of these losses. The present study provides a better understanding of the seepage behavior within and between these canals throughout the irrigation area, as these canals pass through a varying landscape, including agricultural fields, steep slopes, marshes, and residential areas. Measurements of the canal seepage were performed from June to October, 2008. The inflow-outflow method was used to measure steady-state seepage loss rates in selected canal reaches, using an acoustic flow meter. As a result, seepage gaining streams, losing streams, and gaining-losing streams were identified. Spatial and temporal variation of the seepage was observed. In this regard, spatial variation was observed along the canals whereby a descending trend of the mean seepage loss was found in the downstream direction. Spatial variation was also found between canals because the reaches on canals located in the eastern part of Logan City presented higher seepage losses than those of the canal reaches in the western part of the city. Moreover, temporal variations were identified in that a monthly comparison of seepage losses within reaches indicated higher seepage losses in late July and August. Additionally, comments about the performance of the acoustic flow meter are presented in this paper