Treatment of Grape Marc Using Earthworms Makes Winery Wastes More Suitable for Crop Fertilizer

This is the 100th post on The Academic Wino!  I’m so excited to hit #100, and am looking forward to the next 100!

For the 100th post, we’re going to get down and dirty….

We’ve covered winery wastes (grape marc) several times throughout our 100 post journey, and today’s post will be a continuation of that field of research.  Winery wastes or grape marc/residues have been looked at for use as meat preservatives, biogas alternatives, for medicinal purposes such as treatments for diabetes and influenza, and also for use as crop fertilizers.

http://www.worms4earth.com/images/euros_in_soil.jpg

As a refresher, grape marc/residue consists of seeds, stalks, pulp, and seeds that remain after the grapes have been pressed in the winemaking process.  In addition to all the uses mentioned above, this marc can be used as a crop fertilizer due to its high concentrations of macro- and micro-nutrients, including nitrogen and potassium.  Overproduction of grape marc in winemaking regions can be problematic, however, as they often lead to poor disposal practices and poorly timed application practices, which can have negative effects on the environment.  Too much winery waste in the environment can release an excess of tannins and phenols into the soil, which could inhibit root growth of plants in the area.

One way to combat these negative effects on the environment could be to stabilize the grape marc prior to using it as a crop fertilizer.  Stabilization occurs when there is decomposition of an organic waste (such as grape marc) to a point where the aforementioned negative effects are markedly reduced, which will occur via decreases in microbial activity and concentrations of labile compounds.  In a nutshell, stabilization works to transform the organic waste into a safer and more stabilized material that is suitable for soil applications.

The two most common ways to achieve organic waste stabilization is by composting and by vermicomposting.  The difference between the two is that vermicomposting involves biooxidation and stabilization of the organic waste that, unlike composting, requires the use of earthworms and microorganisms and doesn’t require a thermophilic stage.  Microorganisms are responsible for producing the enzymes that facilitates the decomposition of the organic wastes; however earthworms play a critical role in ingesting and breaking up the organic matter that subsequently stimulates the microbial populations by creating a greater surface area for colonization and altering the soil biological activity.

The current study reviewed today aimed to evaluate the effectiveness of active phase vermicomposting, which is the phase that involves earthworm activity, for short-term stabilization of grape marc.  Based on previous study’s findings that earthworm activity accelerates the decomposition rates of organic wastes during vermicomposition, the authors of the current study hypothesized that this should result in reduced microbial biomass and activity, and lower enzyme activities compared to a no-earthworm control.  They also hypothesized that these reductions would result in more stabilized grape marc waste after the active phase of vermicomposition.

Methods

Grape marc was obtained from a vineyard in Pontevedra in Galicia, NW Spain, and was then homogenized and stored at 5oC until use.  It was turned for aeration purposes and moistened with water two days prior to the experiment.

Vermicomposting took place in mesocosms that were created by plastic containers that were filled to three quarters full with moistened (80% moisture content) and mature vermicompost in order to ensure survival of the earthworms. 

500 juvenile and adult earthworms (Eisenia andrei, 220+/-14g fresh weight per container) were placed on the surface of the vermicompost.

1kg of grape marc was placed on a mesh (5mm pore size) on the surface of the vermicompost and wet with 20mL of tap water.  The mesh was used to avoid mixing of the vermicompost and the grape marc, as well as easing the separation of the two after the grape marc was processed by the earthworms. 

The mesocosms were covered with perforated lids and placed in an incubation chamber at 20oC and 90% relative humidity.  The control treatment was nearly identical, except that the mesocosm did not include any earthworms.  Each treatment was replicated 5 times. 

Grape marc was completed processed by the earthworms in 15 days.  After this time, samples were collected for analysis by running them through a sieve.

The following chemical analyses were performed on samples:  electrical conductivity, pH, total carbon, total nitrogen, dissolved organic carbon, inorganic nitrogen (NH4+ and NO3-), cellulose, hemicellulose, and lignin contents.

The following microbiological and biochemical analyses were performed on the samples:  bacterial and fungal biomass, total lipidic extract, neutral lipids, glycolipids, phospholipids, total microbial activity, protease activity, and cellulase activity.

Results

  •       The presence of earthworms resulted in a decrease in the labile C pool (dissolved organic carbon) of grape marc.

o   DOC composition may play an important role in determining the stabilization process.

  •       The presence of earthworms resulted in a reduction in cellulose.

o   These results are consistent with other research showing that earthworms accelerate the decomposition rate of organic wastes during vermicomposition.

  •       There were no significant differences between the earthworm-treated grape marc and the no-earthworm controls in regards to hemicellulose, lignin, and the C to N ratio.

o   Other studies have found these are not good indicators of stabilization of organic matter since the values are variable and change irregularly over time.

  •       Earthworm activity increased concentrations of NH4+ compared with the no-earthworm control. 

o   This is likely due to the fact that NH4+ is a secretion of earthworms.

  •       There was no difference in NO3- concentrations between the earthworm-treated grape marc and the no-earthworm control.
  •       Earthworm activity reduced the abundance of bacterial and fungal biomarkers after 15 days of vermicomposting, compared with the control.
  •       Earthworm activity reduced the total microbial activity of grape marc after 15 days of vermicomposting, compared with the control.

o   These results suggest that earthworms favor the stabilization of grape marc.

  •       Earthworm activity reduced the activities of protease and cellulase enzymes.

o   These results go hand in hand with the microbial activity data.

§  These results suggest that a higher degree to stability was reached after active phase vermicomposting with earthworms.

Conclusions

Based on the results of this study, the authors claim that the activity of earthworms (species E. andrei) favored stabilization of grape marc after 15 days of vermicomposting.  This conclusion is reflected in the lower concentration of the labile carbon pool, and lower microbial biomass and activity when compared with the no-earthworm control.  These results could have profound implications on the development of vermicomposting as a preferred method for treating winery wastes for disposal, which would ultimately have profound effects on the environment in which those wastes were applied.

I’d love to hear what you all think of this short study.  Please feel free to leave your comments below!

Source: Gómez-Brandón, M., Lazcano, C., Lores, M., and Domínguez, J. 2011. Short-term stabilization of grape marc through earthworms. Journal of Hazardous Materials 187: 291-295.

DOI: 10.1016/j.jhazmat.2011.01.011
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2 comments for “Treatment of Grape Marc Using Earthworms Makes Winery Wastes More Suitable for Crop Fertilizer

  1. Robert C
    September 15, 2012 at 9:46 am

    Isn’t the grape marc pretty high in acidity? What about the alcohol content in the marc? I would think that would create an inhospitible environment to the worms. Was the marc pre-composted?

    • Becca
      September 15, 2012 at 9:46 am

      Hi Robert,

      Great questions! Here’s the breakdown of the grape marc chemical analysis provided in the original paper:

      pH: 7.77 (so, actually a little basic!)
      Electrical conductivity: 0.28mS/cm2
      Dissolved organic carbon: 0.005g/g
      Cellulose: 0.175g/g
      Hemicellulose: 0.069g/g
      Lignin: 0.517g/g
      C to N ratio: 14.37
      NH4+: 0.0002g/g
      NO3-: 0.00008g/g

      There didn’t seem to be any report of the alcohol content of the marc. The authors did not report any large-scale die-off, so I imagine the conditions were just fine for the earthworms. As far as I can tell, the marc was not pre-composted.

      Hope this helps!

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