Halloween pumpkins are a source of energy, but also a threat to the climate

Rotting pumpkin Halloween decorations emit methane, a greenhouse gas more harmful to the climate than CO2. Up to 22 million pumpkins are thrown away in the UK each year, yet according to the Environmental Protection Institute, biogas produced from just 100,000 pumpkins provides enough energy for 10,000 homes for 24 hours.

The Institute for Environmental Protection – National Research Institute – has published a report demonstrating how Halloween affects food waste. Citing the British organization Hubbub, the Institute reports that in 2024, during the environmental campaign, approximately 100,000 discarded pumpkins were collected and converted into biogas, generating enough energy to power 10,000 homes for one day. Meanwhile, estimates suggest that Britons waste between 15 and 22 million pumpkins annually, and this number is growing year by year.

According to the Institute of Environmental Protection (IOŚ) report, pumpkins purchased for autumn decorations, including Halloween, later end up in the trash, even though their flesh and seeds are considered wholesome food.

"They undergo anaerobic decomposition, producing methane – a greenhouse gas with a much higher global warming potential (GWP) than carbon dioxide. In this way, the seemingly innocent tradition of decorating pumpkins contributes to greenhouse gas emissions and economic losses," the Institute of Environmental Protection wrote in the report.

According to the Institute of Environmental Protection (IOŚ), pumpkins should be used as animal feed, and if they show signs of spoilage, they can be converted into biogas through anaerobic fermentation and used to produce electricity, heat, or fuel. However, this requires an appropriate system for segregating and directing organic waste to a biogas plant.

Dr. Eng. Anna Klepacz-Smółka from the Faculty of Process Engineering and Environmental Protection at the Lodz University of Technology admitted in an interview with PAP that, taking into account the economies of scale, used pumpkins are biowaste that can be an excellent substrate for a biogas plant.

"The problem, however, is the dispersion of the product among homes. A global idea could be a pumpkin collection organized, for example, by municipalities or as part of a social campaign to raise awareness of the enormous potential hidden in biowaste and the importance of selective collection," Klepacz-Smółka told PAP.

The Institute of Environmental Protection claims that in 2024, British and European cities have already started pilot programmes for collecting pumpkin waste as part of selective biowaste collection, which could be an inspiration for local governments in Poland.

"Every unused pumpkin is not only a wasted food product, but also a waste of water, energy, and labor put into its production. Producing 1 kg of pumpkin in Polish conditions requires 150 to 250 liters of water," emphasizes Dr. Sylwia Łaba from the Institute of Environmental Protection – National Research Institute, who heads the SMART-FOOD project.

She added that this is particularly important given the scale of food waste in Poland. As much as 4.65 million tons of food waste are generated annually, over 2.5 million tons of which comes from households.

In its report, the Institute of Environmental Protection (IOŚ) advises that instead of purchasing pumpkins solely for ornamental purposes, choose edible or oil-producing varieties, which can be used to make soups, cakes, breads, or curries. Pumpkin seeds have numerous health benefits – they help regulate blood sugar and cholesterol levels, and the zinc they contain supports the immune system.

Klepacz-Smółka confirmed that this is a good direction, but emphasized that it would be necessary to analyze whether the yield from adding pumpkins to biogas production would offset the fuel used to transport the harvested pumpkins to the biogas plant. "Therefore, local biogas plants should be considered," she added.

Prof. Janina Gajc-Wolska from the Warsaw University of Life Sciences said in an interview with PAP that pumpkins can be used to produce animal feed, and ground pumpkin remains can be incorporated into the soil, fertilizing it.

– If someone has their own house and garden, composting used pumpkins and using them as valuable fertilizer is the simplest and ecological way to manage them – Klepacz-Smółka said in an interview with PAP.

According to the Institute of Environmental Protection (IOŚ), food waste remains one of the most serious environmental problems facing the world today. The Institute cited data from the European Commission and UNEP, which indicate that approximately one-third of all food produced globally is thrown away – over 1.3 billion tons per year. In Poland, according to IOŚ-PIB data submitted to Eurostat, approximately 4.7 million tons of food waste are generated annually, the largest share of which is fruit and vegetables.

The Institute of Environmental Protection (IOŚ) reported that in Poland, the area under pumpkin cultivation increased from 1,100 hectares to approximately 8,900 hectares between 2014 and 2022, achieving a yield of nearly 400,000 tons annually. According to European statistics, in 2024, Poland was the leader in pumpkin production in Europe, ahead of France, Spain, and Germany. (PAP)

jus/ malk/ mhr/