Renewable energy development.
Among many renewable energy sources solar thermal and photovoltaic collectors are still not mature and are cost-prohibitive. For instance, energy conversion efficiency of the photovoltaic modules available in the market is at the maximum of 15%. Photovoltaic cells are also referred to as solar energy harvesting factories with an input to output ratios of 1:7. The return energy production rate from the photovoltaic modules is slow over 20-25 years . Wind and geothermal sources have limitations such as location, availability, and intensity. Since most of the transportation and industrial sectors need liquid fuels to drive the machinery and engines, more emphasis is needed on alternative fuel sources such as bio diesel. Bio diesel is composed of methyl or ethyl esters produced from vegetable oil or animal oil and has fuel properties similar to diesel fuel which renders its use as bio fuel. Bio diesel offers many benefits:
a serves as alternative to petroleum-derived fuel, which implies a lower dependence on crude oil foreign imports; b provides favourable energy return on energy invested;
c reduces greenhouse emissions .
The combined pressures of rising fuel prices, diminishing global supplies of crude oil and legislation to control climate change by reducing greenhouse-gas emissions has resulted in both aggressive renewable fuel policies and a rapid growth in the emerging bio fuels industry.
As a result surplus agricultural feedstock's in the US and Europe are quickly being exhausted, contributing to commodity price increases.
As a result of the foregoing there has been a growing acknowledgement of, and emphasis on, next-generation type such as cellulose ethanol, algae-derived bio diesel and hydrolysis oil (bio-oil) from woody biomass. More recently, attention has turned to more advanced bio fuels made from renewable waste resources. These more advanced bio fuels, renewable diesel, gasoline and jet fuel are literally seen as a replacements for today's diesel, gasoline and jet fuel products.
Thermo chemical conversion routes produced energy dense bio-oil (35-37 MJ/kg) that approached shale oil (41 MJ/kg). Bio diesel has about 80% the energy density of kerosene but has the potential of being chemically converted into kerosene, the basic component of jet fuel. Jet fuel now accounts for about 8% of the petroleum use with very few renewable alternatives. Ethanol is not dense enough with only half the energy per volume of the jet fuel.
The residual biomass from oil extraction can be partly used as high protein animal feed and, possibly, as source of small amounts of other high-value micro algal products.
The use of bio ethanol as an alternative steadily increases around the world. Accordingly, there have been significantly increasing endeavours on the technology development that facilitate the transformation of bio renewable into transportation fuels.
To meet this end, many technologies have employed sugar- and corn-based biomass for the industrial production of bio ethanol, especially in Brazil and U. S., respectively.
While they contributed a lot to the commercialisation process, the viability of the so-called 1st generation bio fuels is somewhat questionable because of their conflict with food supply.
The key factor influencing bio fuel efficacy is whether native ecosystems can be maintained or not. No matter how effective biomass is for producing ethanol, its benefits quickly decrease if all the tropical forests are being razed to make energy crops, leading to another type of a large amount of greenhouse gas (GHG) emission pathway. To solve this crisis, a new type of biomass is now being developed and their bio fuels can be produced locally in sustainable systems.
The seaweeds (macro algae) and micro algae be an excellent alternative raw material as a new marine biomass for bio fuel production growing along the shallow coastal area of many countries and easy to cultivate.
It mainly consists of polysaccharide complexes of fibres and agar whose basic monomer is glucose and galactose residue, respectively. Generally, there are five major bottom lines for a bio ethanol process to be economically viable: the feedstock
must be plentiful, inexpensive, in high energy conversion rate, in low demand for food industry, and finally, has to be cultivated in sustainable systems.
Most seaweed shows very fast growing rate (4 - 6 harvest cycles per year) with high CO2 fixation ability, which is 5 - 7 times higher than that of a land plant.
Furthermore, they can be mass cultivated using seawater and free sunlight without any need of nitrogen-based fertilizer which has been a significant source of GHG that also destroys stratospheric ozone. In addition, they do not contain any lignin that has to be eliminated prior to hydrolysis step, which has been a major obstacle to increase production cost in lignocelluloses process.
Furthermore, the seaweed has ability to absorb nitrogen and phosphorous thereby purifying sea water which leads to oceans' sustainability/health.
Solid bio fuels have a low energy density, which limits the commercial application to locations close to the place of production and in our case Ireland shores. One way to solve this problem is the conversion of this feedstock into liquid fuel. These liquids have a much higher energy density and are easy to store and transport. The technology employed to convert wet biomass material to liquid fuel now in development.
This technology is believed to mimic the natural geological processes thought to be involved in the formation of fossil fuel, but in the time scale of hours or even minutes. A number of technical terminologies have been used in the literature to refer
to this technology, but it essentially utilize high temperature or the high activity of water in sub-critical conditions in order to decompose biomass materials down to shorter and smaller molecular materials with a higher energy density or more valuable chemicals/feed.
Movement From a hydrocarbon society to carbohydrate society.
There are two main routes or processes, dry-milling of seaweed and algae most common in sub-tropical and tropical regions.
Dried seaweed can be stored and kept for a long time but you need energy (sun). The wet processing methods better suited in sea climate regions like Ireland, Iceland, Scotland for example. Using dried seaweed or algae can easily and commercially converted into bio-crude and petroleum and diesel by piralysis. In the wet-conversion process, the seaweed are converted into
crude and other products using high pressure and increased temperatures. About half is converted into bio-crude and the rest stays behind in the water as solids which allows for the production of multiple food and industrial products including starch, proteins, fructose, oil and ethanol, nutracell, medicine, pharmaceutical and cosmetics.
Large quantities of algal biomass needed for the production of biodiesel could be grown in photo bioreactors combined with photonics and biotechnologies and offshore.
The direct hydrothermal liquefaction is currently the most energy efficient technique for producing biodiesel from algae without the need to reduce the water content of the algal biomass, which is high in average about 80%. The overall approach would adopt an integrated biomass-production conversion system. In addition to oil there is gas and steam, the oil part will contain about half of the energy part the rest is still dissolved in the water.