Marc, a new resource

Apertura_portaleWaste is the problem of this century. In the previous century, primary concern was to produce… and residual products turned up in the garbage can. Then, people realized that waste could have value and the first system for enhancing the agricultural product has been the energetic one. However, energy is a commodity, a lot of it is needed, but the economic value per kWh is low. Since nature places in the grapes many valuable molecules, before arriving to energy enhancement it is necessary to recover whatever is possible and has high added value”. With these words Maurizio Masi, Director of Giulio Natta Department of Chemistry of Materials and Chemical Engineering at the Polytechnic of Milan, on July 2015 gave way to the conference held in order to present the results obtained by research groups from six Italian Universities within the project whose title was Valorizzazione dei sottoprodotti e dei residui di vinificazione tramite estrazione e produzione di molecole ad alto valore aggiunto (Enhancement of by-products and leftovers of winemaking through the extraction and production of molecules with high added value). The project is co-funded by Ager – Agroalimentare e Ricerca (Agribusiness and Research).

Biorefinery Project

The need to adapt to CMO Reform for wine (see box) concerning disposal of by-products of winemaking and the awareness that wine industry has such numbers that justify specific searches led to Biorefinery Project. Carla Da Porto, Professor at the Department of Scienza degli Alimenti (Food Science), University of Udine, and coordinator of this project, of which her University is leader, highlighted: “Our aim consisted in applying to the wine sector a model of biorefinery, in order to create a new integrated, highly profitable system for promoting “smart” disposal of waste characterized by high environmental impact, which can be exploited and utilized in other industrial sectors than the oenological one“.
In what could be defined as industrial logic, a cascade approach was chosen in the use of by-products. Carla Da Porto highlighted: “The waste of one or more operational units mostly were the raw material for the next unit, in order to completely consume all present substances. Among the many by-products of the oenological industry, we chose to focus on skins and grape seeds, because they contain the most interesting active components: in the skins there are polyphenols, which can be employed in the domain of food (and supplements) as natural antioxidants, but also in both cosmetic and pharmaceutical sectors“.
The waste of vine and wine industry are numerous: pruning wood, stems, marc, lees and wastewater. Attilio Citterio, Professor at Giulio Natta CMIC Department of the Polytechnic of Milan, told: “If one wanted to use them only for the production of bioethanol, the industry could rarely obtain productions characterized by large volume and low cost, so that this road could be sustainable. In my opinion, it is necessary to make different choices, which pursue uses that take into account the actual availability of the raw material in order to create credible industries. Therefore, it is better to work on a smaller scale, but with higher added value“.

From extraction…

That is why the first stage of this project involved the extraction from marc of the more interesting components. The working group of the Polytechnic has used some different technologies in an integrated manner, in order to obtain as many by-products as possible. Citterio explained: “Our target were both phenolic compounds and bioactive proteins (from peel and seed). The first stage was the evaluation of different extraction methods. By using microwaves with ethanol and with pulsed technique, we recovered 5.2% of polyphenols from skins and 22.5% by seeds deprived from lipid component”. The working group of the University of Udine, within the project concerning extraction techniques, deepened the one concerning supercritical technique with carbon dioxide. Supercritical fluid is a substance that – under certain conditions of temperature and pressure – has intermediate properties between those of gases and liquids. Therefore, it is excellent green solvent. Carla Da Porto explained: “Supercritical carbon dioxide, under moderate critical pressure and temperature, is neither flammable nor toxic, it is chemically inert and recyclable after the process (more than 95% of it is recovered). The disadvantage is represented by high initial costs for the plant, but the higher yields in the extraction compared to other more traditional methods make the amortization fast enough, if the plant is used for extracting compounds characterized by high added value“.

… to application

At a later time, it was necessary to verify if the market value of these compounds could justify their extraction. Biorefinery Project also dealt with this issue.
As for proteins, for example, among the ones extracted from the grape skins there is a very interesting category, defensins. Citterio explained: “They protect grapes from fungal attack and could be used in agriculture in order to protect crops. Other proteins are used to feed livestock or even human beings“.


This research focused on phenolic component, because these antioxidant compounds are part of the composition of functional foods and supplements. But do phenols of marc really have the so praised effects? In order to understand this, the working group of Parma characterized them as well as their potential effect on human health. Daniele del Rio, Professor at the Department of Scienza degli Alimenti (Food Science) of the University of Parma, explained: “Polyphenolic compounds are among the classes of substances that seem to counteract the action of numerous negative behaviours that cause the loss of years of life. However, it is not simple to prove it in an absolute sense, because epidemiological studies do not allow giving absolute certainties; sometimes they even contradict each other. In any case, there is widespread tendency to include them in foods, supplements and functional foods. In Japan some swimming-pools are even filled with red wine“. With his staff, using phenolic compounds extracted by his colleagues in Udine and Milan, Del Rio simulated in vitro the biotransformation these compounds undergo in our body as well as effects of the so obtained metabolites on physiological mechanisms. Some of them may exert a preventive action against chronic diseases.


With a view to cascade approach, again, the residual material from extraction of phenolic compounds was sent to the University of Bologna, which took care of studying the potential use of this substrate in the chain of biopolymers. Lorenzo Bertin, Professor at the Department of Civil, Chemical, Environmental and Material Engineering (Dipartimento di Ingegneria Civile, Chimica, Ambientale e dei Materiali – DICAM) of the University of Bologna said: “The production of polymers of non-fossil origin is growing at a higher rate than any other sector. We have focused on Polyhydroxyalkanoates (PHA): a class of microbial polymers that are produced and accumulated by some microorganisms as a source of carbon and energy“.
These polymers have different applications: they are used pure in order to obtain plastics by extrusion, potentially alternative to polypropylene (PP); as co-polymers for more ductile and workable and less fragile plastic materials, which can be also employed in the packaging sector. Mixed with different polymers, also not bio-based ones, they can be used in the production of many plastics. Lorenzo Bertin explained: “The problem with this bio-polymer is its cost, closely linked to the price“. That is why it was decided to evaluate the use of oenological dephenolized residues and the feasibility of the thing was proven, by developing a biotechnological process in two stages, in which the organic residue was first acidified. The acid effluent was employed as carbon source for the accumulation of polymer in microbial cells.

Finally, energy

What remained after this latest treatment was sent to the two groups that were active on the production of energy. Alessandra D’Epifanio, Professor at the Department of Chemical Science and Technology, Tor Vergata University of Rome, said: “For each litre of wine, 1.8 litres of waste water are produced, which by their acidity and organic richness have a high environmental impact“. For this reason, alongside with their colleagues at the University of Milan, the possibility of creating reactors that produce bio-electric energy and biohydrogen from residues of the winemaking process was investigated. This way is feasible, but it cannot be realized by using lees as they are. Roberto Oberti, (DiSAA- UniMI), said: “The use of lees as they are as an energy substrate is not compatible with the considered processes, although the white ones, with higher content in sugars and lower level of polyphenols and other inhibitors, show a best overall compatibility in comparison with the red ones. In the production of biohydrogen by fermentation, however, a beneficial effect is obtained by mixing the waste from winemaking with manure“. In this area, therefore, there is room for collaboration with different chains.

Wine Common Market Organisation Reform (provided in both 479/2008 and 555/2008 EC Regulations) outlined for the by-products of wine a scenario for their gradual decrease, up to the disappearance of the aid to this sector through mandatory distillation. The question is very important in relation to the quantities of by-products that many Countries, Italy in the lead, will have to manage in a different way than they did until now. As a matter of fact, the producers of wine were obliged to give marc for the production of ethanol and extraction of grape seed oil. With the reduction of financial aid, they will have to face the problem of disposal, particularly as the overall EU legislation concerning waste (2006/12/EC Directive) requires Member States to adopt the necessary measures to ensure that waste is disposed or recycled without endangering human health and without using processes or methods harmful to the environment.

According to data released by the International Organization of Vine and Wine, OIV, the world wine production in 2014 was 271 million hectolitres, of which 44.4 in Italy, second largest producer after France. It is necessary to discuss these volumes, in order to understand which amount of by-products result from them. Carla Da Porto highlighted: “100 kg of grapes originate about 25 kg marc (of which 50% skins, 25% seeds, 25% stalks). As for Italian wine production in 2014, in order to produce 44 million hectolitres of wine, about 6 million tonnes of grapes were used, which generated 1.5 million tonnes of marc as by-products. A third of this quantity must be excluded, because it enters the production process of grappa. The remaining 1 million tonnes of marc is the amount that in 2014 could have been used according to the guidelines outlined in Biorefinery Project“.

Article by Elena Consonni

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