The new frontier of hurricane resilience: harmful algal blooms

After hurricanes strike, toxic algae can bloom. AECOM’s Vice President Dan Levy explains the magnitude of this environmental challenge and how our teams are helping confront it.

When Hurricane Irma struck Florida in 2017, it inflicted tens of billions of dollars in damages. Yet, after the storm subsided, communities were confronted with a new environmental hazard: harmful algal blooms (HABs).

HABs occur when aquatic algae grow to excessive levels, often producing toxins that threaten human health and ecosystems. In the wake of Irma, HABs bloomed rapidly across the state and, by the following summer, covered nearly the entire surface of Florida’s largest lake, Lake Okeechobee, causing more than $300 million in losses.

Increasingly, it’s clear that hurricanes like Irma are contributing to HABs. But what’s behind the connection? We’re working with communities across Florida to address this issue using groundbreaking technologies — even helping turn these toxic algae into net zero fuel. Here are some of our key learnings.

Behind the Bloom

Over the past decade, HABs have been spreading geographically, occurring more frequently, lasting longer, and increasing in toxicity. One of the primary causes is nutrient pollution, which occurs when excessive amounts of nutrients such as phosphorus and nitrogen enter bodies of water through runoff from agricultural practices, wastewater treatment plants, and urbanization. These nutrients act as a fertilizer for algae, causing them to grow and multiply rapidly, leading to the formation of HABs.

The toxic byproducts produced by HABs harm flora and fauna, causing business closures, reductions in property values, higher costs to treat drinking water, loss of tourism and even fatalities among animals, such as dogs that come in contact with the effected water. By economic numbers, HABs are as devastating as any natural disaster, inflicting an estimated $1 billion in damages to the U.S. tourism industry each year.

And like many other natural disasters, HABs are also intertwined with climate change.

Algae thrive in warmer waters, and as water temperatures continue to rise, HABS are predicted to become more prevalent. Those higher temperatures are also leading to more frequent and intense weather events—which threaten to exacerbate HABs further.

Due to the flooding that accompanies them, hurricanes generate considerable runoff, directing even more nutrients into bodies of water. As that runoff pours in, heavy winds can also disturb and release nutrients stored in lake and riverbed sediments, compounding the problem.

These HABs flourish amidst the climate crisis, as well as contribute to it.

Upon decomposition, these massive blooms release significant amounts of carbon dioxide as well as more potent greenhouse gases like methane and nitrous oxide. Researchers estimate that eutrophication (the greening of freshwater lakes due to excess algae) will increase the release of methane into the atmosphere by 30-90 % during the next century.

In essence, HABs are a climate crisis feedback loop, much like melting glaciers or thawing permafrost. And in Florida, where warming waters and worsening storms have collided, algae have turned into an environmental crisis.

Outlining solutions

In the past decade, HABs have caused hundreds of millions of dollars in damages in Florida. Blooms have even spanned close to a thousand miles during the state’s 2018 destructive algae episodes.

But the state has also become a test bed for new solutions, and we’ve had the opportunity to design numerous innovations across the state. In the process, we’ve also identified two key interventions needed to mitigate HABs.

The first is better planning and resilience. New HAB monitoring and prediction approaches have been successfully deployed, yet the results need to be factored adequately into stormwater management and hurricane response and recovery.

Today, it’s critical to integrate the risk of HABs into the infrastructure we build and the funds we allocate to address natural hazards. Hurricane-prone states can start by updating their State’s Division of Emergency Management Hurricane Loss and Mitigation Program to include HAB mitigation in their resilience and recovery funds.

The second is proactive mitigation of HABs. This is perhaps the more challenging task, as it involves extracting algae and excessive nutrients from polluted water without adversely impacting ecosystems. To tackle this engineering challenge, our teams have had to create novel technologies.

One method we’ve developed is to harvest the excessive algae, and the nutrients that support it, using new breakthrough technology. Our Hydronucleation Flotation Technology (HFT) is an example of this approach. It employs a multistage system that effectively separates and extracts algae from the water and returns clean clarified water to its source, safely and sustainably. By physically removing algae without damaging the cells, the key nutrients that fuel algal growth (phosphorus and nitrogen) are also removed along with carbon and algal toxins that might be present. By reducing the nutrients, the threat of future HABs can be reduced and potentially eliminated.

Once toxic. Now net zero.

Algae extraction is just a starting point. In collaboration with state and federal governments, we’re also incorporating another breakthrough technology known as Hydrothermal Processing that transforms the recovered algae biomass (wet waste) into “carbon neutral” energy, biocrude oil and Renewable Natural Gas (RNG), to help reduce our dependance on fossil fuels.

The process uses heat and pressure similar to how fossil crude oil is formed naturally—but does so in 30 minutes instead of millions of years. The result is a carbon neutral biofuel that’s functionally equivalent to its fossil counterparts.

We recently conducted the first ever field-scale algae to biocrude oil demonstration project in the US. The project was conducted on a drinking water reservoir in Ohio that was plagued with HABs. It was proven highly effective and demonstrated how innovative “breakthrough” technologies can be coupled to deliver a sustainable closed loop solution with virtually little to no waste.

Reframing resilience.

Despite significant progress in areas like Florida to reduce the supply of nutrients to our waterways, HABs continue to pose threats to communities and ecosystems nationwide. To tackle them, policy makers will need to be proactive.

As vulnerable regions update wind and flood maps to adapt to stronger storms, they must consider HABs in decision making. And in the wake of hurricanes and other natural hazards, HAB mitigation will be essential to protect public health and our valuable waterways.

But most importantly, the nation needs a paradigm shift. Today, HABs have become a new frontier of storm resilience. To tame them, policymakers must now center them in their infrastructure conversations.