A huge demand has developed for oil for biodiesel and now also for aviation biofuel, but finding a sustainable source has been hard.
Oil palm is sturdy and highly productive, but grows best in wet tropical areas, and vast swaths of rainforest have been razed to make way for it. Jatropha also raised hopes, because it can grow in poor soil with minimal inputs, but it turned out not to be as hardy and self-sufficient as initially thought.
Now, Acrocomia aculeata, also called macaúba or macaw palm, is gaining attention as a potential sustainable biomass feedstock, particularly for biofuel. A newly published paper says the tree has promise, but also faces significant risks, and more study must be done before attempting commercial cultivation.
A common source of oil, and more
The macaw palm is common from Florida through South America. It has been used traditionally for food, fodder, fibre, medicine and soap. Recent studies have shown that oil extracted from the pulp of the plant’s fruit has great potential for use as biofuel, while oil from the pit is good for cosmetics and food products. In addition, the press cake left over after oil extraction is good for animal feed, and the shell of the pit can be used as fuel or for producing activated charcoal.
It appears to grow well in areas that have been disturbed by human activity and have meagre resources, such as degraded pastures and along roads. That’s important to ensuring its use for biofuel wouldn’t displace other land uses. It also helps that the largest natural populations are in Brazil, one of the world leaders in biofuels production.
“It has relatively high yields, even in natural stands,” says Rob Bailis, an SEI-US senior scientist who co-authored the paper. “So that with some effort to breed high-yielding cultivars, production could rival palm oil, but with far fewer negative impacts.”
Large-scale cultivation of African oil palm has been linked to deforestation and land grabs. notes Mirco Plath, who co-authored the macaw palm study while working as a researcher in a project on bioenergy at Leuphana University, in Lüneburg, Germany, points out that recent research in Latin America has shown native species like the macaw palm can have fewer negative effects on local biodiversity and ecosystems, fulfil traditional services to local landholders (such as supplying oil and animal feed), and require less investment by eliminating dependence on external seed sources and foreign technologies.
Assessing the macaw palm
Despite these apparent advantages, the macaw palm is still limited to small-scale extraction, although Brazilian researchers have carried out numerous studies in recent years, and the Brazilian state government of Minas Gerais has enacted policies to stimulate use for producing biokerosene for aviation.
There has been little study of where and how well the macaw palm could be cultivated, and how it performs under differing environmental conditions, according to the new paper. That’s why researchers set out to get a clearer picture of the tree’s potential in Central and South America.
The researchers searched through scientific studies and data to find 271 recorded occurrences of the macaw palm, used these occurrences to come up with 19 climate and 17 soil factors that predict where the tree could thrive, and then mapped its potential distribution. They also studied the potential impact of climate change on macaw palm cultivation – an important consideration given that the tree must grow for four to five years before starting to flower and produce commercial yields, and then will continue to produce for decades.
The researchers found a total potential distribution area of about 3.68 million km2 for the macaw palm in Latin America and Florida – particularly in Central America, northern Colombia and Venezuela, southern Brazil and eastern Paraguay.
Savannas make up the largest share of this suitable land, 42.6%, and highest predicted habitat suitability. The macaw palm is particularly prevalent on pastures, showing potential for local producers to grow it in stands around cattle, creating an extra source of income, the researchers found.
Nearly all regions potentially suitable for the macaw palm are outside of the tropical rainforests along the Amazon Basin in Brazil, Bolivia, Colombia and Peru, Plath notes. This contrasts with the African oil palm, “which has become one of the major driver for deforestation in the tropics for the last decades”, he says.
All of this adds up to a lot of promise for the macaw palm, Bailis says. “Given that it grows on human-impacted lands, is compatible with extensive livestock production, produces other marketable products and has potentially high yields, it is worth additional research and pilot testing.”
One big potential problem is that much of the land predicted to be suitable for macaw palm cultivation is in areas with high conservation value, such as wetlands, subtropical forest systems and savannas (including the threatened cerrado in Brazil).
Plath added that the study’s modelling supports recent studies showing extensive occurrence of the macaw palm in nutrient-rich soils. If it is more productive in such soils, large-scale cultivation could compete with food production, while cultivation in poorer soils could require more inputs and/or labour to be viable.
Furthermore, changes predicted under an Intergovernmental Panel on Climate Change “business as usual” emission scenario could cause the loss of 59% of the areas currently deemed potentially suitable for the macaw palm, while making many of the remaining areas less suitable, the researchers reported.
More study needed
Jumping into large-scale production too quickly risks a repeat of Jatropha, Plath warns. “Since the initial wave of excitement about Jatropha broke in around 2008, many projects have failed. Not only did ‘green investors’ lose money, also local communities and smallholders in developing countries were put at risk.”
One major challenge for macaw palm cultivation is that trees variability widely in the quantity and quality of oil they produce, Plath reports. The researchers, for instance, found reported oil yields ranging from 0.6 to 7.5 tonnes per hectare.
This variability could provide genetic materials that could help develop the tree, “but the way to successfully breed this species and to achieve a permanent and constant yield in palms is probably long,” Plath adds. “Despite a considerable research by Brazilian research institutions in recent years, there is still a crucial knowledge gap about the ecological requirements of this palm species, its performance under cultivated conditions, and differing cultivation practices as well as the socio-economic benefits it may provide.”
In other words, the macaw palm shows promise, but it’s not time to declare it the next biofuel source of the future.