Finding A Sustainable Use For Winery Waste

In public transportation, power generation gen-sets, or pumps in farms, Compression Ignition (CI) engines are generally preferred as they are more efficient and cheaper. However, diesel is non-renewable and is also the primary source of particulate matter (PM) emissions which can cause adverse health problems. Biofuels that seem to be the possible key solution for the present challenge can be obtained from a variety of sources like food, non-food feedstocks, microalgae, and other biomass wastes.

Attempts have been made earlier by many researchers to improve the quality of such oils by blending them with low viscous fuels or by inducting secondary gaseous fuels such as biogas, producer gas, LPG, hydrogen, etc. As far as hydrogen as a secondary fuel is concerned, it has both favorable as well as unfavorable properties for engine fuels, which are radically different from conventional fuels. The very high flame velocity of hydrogen makes the combustion approach the theoretical Otto cycle in an SI engine, but the same property, along with other properties such as low ignition energy and wide combustion limits, poses the problem of flash-back in an engine.

Several articles related to the winery industry confirms that wineries all over the world are growing in number each year and the amount of residue and waste generated from the winery industry keeps increasing. It is estimated that global wine production leaves nearly thirteen million tons of grape marc waste each year and is generally disposed of at a cost to the winery in many parts of the globe.

Approximately about 25% of the weight results in the accumulation of byproduct/wastes. Among this, grape stalk and grape marc are the primary wastes of wine production; the grape stalk is obtained after the de-stemming process and contains the stems of the grape, while grape marc, obtained after the pressing process, consists of processed skins and seeds. In addition, winery wastewater that comes from the water used in the different steps of wine production contains remains of grape pulp, skin, and seeds. The main problem of all these organic materials is their disposal and treatment, which poses difficulty in their management.

Conversion of the useless waste into a usable source of energy would be a potential option since grape marc residue is readily available and can be sourced at comparatively lower costs, making it economically viable. In addition, it has the dual benefits of serving not only as an alternative to the conventional fossil fuels but also reduces both the greenhouse gas emissions and the hardships involved in the disposal of the wastes. Considering the amount of waste generated, one viable alternative that can be thought of is the extraction of oil from the seeds that can be used as an alternative source of energy for internal combustion engine application.

In view of the above facts, an attempt was made by Prabhu Chelladorai to use biofuel obtained from winery industry waste (grapeseed oil) as pilot fuel in compression ignition engines. Further, the synergistic effect of inducting hydrogen on the performance, emission, and combustion characteristics of diesel, grape seed biodiesel (GSBD), and neat grapeseed oil (NGSO) as pilot fuel were studied. The experiments were conducted at 50% and 100% loads with a constant engine speed of 1500 rpm. However, the extent of induction was limited to the point beyond which there is a propensity to knock. The following conclusions were drawn based on the experimental results.

The performance of the diesel engine with neat grapeseed oil is poor as indicated by lower brake thermal efficiency of 25.94% and higher smoke opacity of 54.9%. When neat grapeseed oil is converted into grapeseed biodiesel, the brake thermal efficiency of engine improves to 30.28% and smoke opacity reduces to 44.1%. However, brake specific Nitric oxide (NO) emission increases from 8.71 g/kWh to 8.92 g/kWh due to improved combustion.

Dual fuelling with hydrogen, however, increases the brake thermal efficiency of all tested fuels as a result of the considerably higher heating value of hydrogen, higher flame velocity and exponentially increasing reaction rates. The maximum energy share of hydrogen at full load is limited to 14.46, 14.1% and 12.8% respectively for diesel, grapeseed biodiesel, and neat grapeseed oil. With an increase in hydrogen energy share, specific energy consumption decreases owing to the significantly higher heating value and superior combustion characteristics.

As a biofuel obtained from winery waste, grape seed biodiesel, in principle, will not only serve as a fuel substitute, the claim of which is reinforced by the above results, that indicates a performance closer to diesel, but will also reduce the quantum of residual waste from winery industry that would otherwise become redundant and finally discharged into the environment or subjected to complicated procedures for degradation. Further, the synergistic effect of hydrogen induction with grapeseed biodiesel in a CI engine is evident from higher brake thermal efficiency of 36.04% and lower smoke opacity of 35.4% within maximum knock limited hydrogen energy share, with an increase in brake specific NO emission from 8.92 g/kWh to 12.81 g/kWh. Brake specific hydrocarbon (HC) and carbon monoxide (CO) emission also reduces as a portion of the hydrocarbon fuel is replaced by carbon-free hydrogen.

These findings are described in the article entitled Synergistic effect of hydrogen induction with biofuel obtained from winery waste (grapeseed oil) for CI engine application, recently published in the International Journal of Hydrogen Energy. This work was conducted by Prabhu Chelladorai, Edwin Geo Varuvel, Leenus J. Martin, and Nagalingam Bedhannan from SRM Institute Of Science And Technology (formerly known as SRM University).