Biodiesel from Microalgae

Jessica Ketchum

Karris Roland

Introduction The depletion of fossil fuels and escalation of CO2

concentration in the atmosphere has shifted the globalinterest to renewable fuels.

Microalgae-derived biodiesel is a clean, sustainableenergy source due to high biomass productivity, rapidlipid accumulation, and ability to survive in harshenvironments.

Algae biodiesel does not include sulfur and diminishesthe release of particulate matter, CO, hydrocarbons,and SOx.

Biodiesel Processing From Microalgae

Harvesting, dewatering and drying have been the main barriers of algal oil production.

“Algal cells are generally too small for traditional means of filtration, centrifuging, or solvent extraction.

Average harvesting concentration (0.1-1%)

Extraction- “Whole Lotta-Watta”

Problem

Attempts to Eliminate Dewatering Forcing Water and Algae to separate from each other

“Milking” algal cell

Getting Algae to concentrate

Must have a solution to this problem:

1 technology/60 days (May 2011-Biofuels Digest)

National Algae Association-”Algae Growing, Harvesting, Extraction Technologies”

New Technology!! 1. Enzymatic Hydrolosis –AER

2. PEF (Electric Pulse)-Diversified Technology (0.1$/gal vs. 1.75$)

3. Amphphillic Solvents -Aurora Algae (US patent 7,868,195)

4. Solid-Liquid Separation-AlgaeVenture Systems (0.007$/gal vs. 3.19$)

5. Single Step and Live Extraction-OriginOil

-Algal cell can heal itself after lysed, for continuous process

We Choose Live Extraction Apply suitable electric field to Algal culture

Volume will depict voltage necessary

---Should be around 20V, way less than PEF (10-30 kV/cm)

Electric Field caused algal cells to release a portion of their algal oil without rupturing

Viable on Commercial Scale?? Cellana-Developer of algae-based feedstocks for

biofuels, animal feed, and Omega-3 nutritional oils.

Announced multi-year off-take for commercial production (Venture w/Neste Oil)

Neste Oil-Worlds leading supplier of renewable biodiesel

Venture to produce commercial scale amounts of Cellana’s ReNew™ Fuel

Sapphire Energy

Sapphire Energy located in Columbus, NM. In 2011, began construction of Crude Farm

Anaerobic Digestion Of Algae Sludge

Used to produce methane from remaining algae feedstock

Anaerobic microbes digest large molecular weight carbon compounds into methane

Reduces handled waste, and recovers unused energy in residual algae feeds

Most common algae species were: Scenedesmus spp. Chlorella spp.

Operated in CSTR with 20 day residence time1,2

Terminal methanogenesis is carried out by specialized group of anaerobic archaea.2

Use of algae for energy (methane production has been investigated since OPEC oil crisis of 1973

Methane Production Methane production mainly influenced by

loading rate and C/N ratio of feed

High loading rates of algae volatile solids (VS), excess algae can inhibit the digestion

Low C/N ratios, cause increased production of ammonia. Inhibits microbe digestion rate

Algae biomass: C/N ratio 6/1

Optimal C/N range 20/1 – 30/13

Typical feed rate for one-stage CSTR: 1.6 [kg VS/(m3 * day)]

Transesterification- Transesterification is the reaction of a fat or oil with alcohol to form

esters and glycerol.

- The triglyceride is a complex molecule that plants and animals use for

storing food energy; simply it is fat.

Transesterification is a multiple stage reaction, where triglycerides are converted to diglycerides, then diglycerides are converted to monoglycerides, and monoglycerides are then converted to esters (biodiesel) and glycerol (by-product).

For the transesterification reaction oil or fat and a short chain alcohol are used as reagents in the presence of a catalyst.

Alcohols that can be used are methanol (most preferred due to its low cost, polar structure, and being the shortest alcohol chain), ethanol, propanol, butanol.

The catalysts can be acid (sulfuric acid, hydrochloric acid), basic (NaOH, KOH) or enzymes. Commercially alkali-catalyzed transesterification is most often utilized since it is faster than acid-catalyzed transesterification.

Transesterification Continued

Parameters influencing the transesterification

reaction rate:

Reaction temperature

Type and amount of catalyst

Mixing intensity

Quality (purity, free fatty acid composition)

Starting materials

Water content

Transesterification Continued

Centrifugation

Centrifugation separates suspended solids from a liquid solution

The biodiesel droplets are separated from the glycerol

A disk centrifuge is a system of rapidly rotating concentric inverted cones placed close together to minimize the time to capture dense particles or liquids while allowing forced flow to continuously add feed and discharge liquids.

Centrifugation Continued

How a disk centrifuge works:

Operates in continuous mode

Feed enters on the axis of rotation and forced to bottom of rotating bowl

Lighter fluid flows up and out of the centrifuge

A nozzle either ejects dense particles or allows build up on outer wall of the bowl

Energy intensive and inefficient harvesting have been major drawbacks in the algae industry

Generally flow rates are > 1 L/min with a high capture rate of 90% and cost about $4.52/L

Increasing the flow rate to > 1 L/min has lower capture rates, but can be offset by larger volumes of culture water, with high culture density and lipid content, processed by the centrifuges and cost $0.864/L

A recent study showed at a rate of 18 L/min by centrifugation lowered the energy consumption by 82% when only 28.5% of algal was harvested.

Centrifugation Continued

References Attached in Paper