introduction

■ Digestive

The DigesTive chapTer examines The meTabolic operaTions of maTerial resources, wheTher living or nonliving. here, meTabolism perTains To physical anD chemical processes, by which maTerial resources are generaTeD, reTaineD, balanceD, reconfigureD, or bioDegraDeD inTo new resources.

Topics of site-remediation techniques for the treatment and reclamation of postindustrial residue or disturbed ecologies have been widely discussed in the last decade within the field of landscape architecture. Bio-remediation and phytoremediation techniques highlight the capacity of plants and associated bacteria to absorb or process harmful chemicals and excess nutrients, granting landscape architecture expanded performance criteria that were previously considered solely within the field of ecology and engineering.

The Digestive chapter examines the metabolic operations of material resources, whether living or nonliving. Here, metabolism pertains to physical and chemical processes, by which material resources are generated, retained, balanced, reconfigured, or biodegraded into new resources. All materials and processes are considered in terms of input and output within a food chain, whether nutritious, innocuous, excessive, or harmful. Within this context, material resources are always in a state of flux. For example, pollutants or excess nutrients are conveyed via air and water flow across site boundaries. Since many contemporary sites are inherited with a history of preceding uses, existing materials such as stone or concrete are often designated for removal offsite. Digestive operations consider migrations of resources as opportunities and constraints for design principles.

Until recently, pollutants or excess materials have been transported offsite to centralized systems for storage (landfill) or processing (sewage treatment plants). With rising energy costs and stricter dumping or discharging protocols, this paradigm has begun to shift to in-situ strategies. In addition, reliance on decentralized and bio-based processes that intend to meet or exceed physical and economic performance has been rapidly increasing, and has been followed by new opportunities for site-specific integration of a spatial, aesthetic, and experiential form.

Sidwell Friends School features a closed-loop system of water recycling, which processes the school’s wastewater in a series of outdoor wetland gardens to be reused within the building. Both the SW 12th Avenue Green Street Project and the Blackstone Stormwater Garden featured in the Fluid chapter incorporate a decentralized bio-based system for integrated stormwater treatment. Designed with a capacity to retain rainfall during storm events, networked planters and bio-swales intercept polluted sediment migration before the sediment reaches nearby water bodies.

Digestive classifies operations in terms of two distinct but congruent scales: micro and macro. Micro encompasses plant, bacterial, or fungal nutrient conversion or uptake; macro defines the larger scale of earthworks, cut and fill, and concealment. Digestive further categorizes such operations according to two distinct time sequences: a one-time operation and an ongoing, managed operation. These scales relate to the sources and locations of materials in a variety of ways.

Water-based resources, such as stormwater surface runoff or building wastewater, are typically categorized within a continual time sequence that requires micro-digestion. For example, the Water-Cleansing Biotope at the DaimlerChrysler Potsdamer Platz plaza continually metabolizes excess nutrients in rainwater collected from 13

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■ unTil recenTly, polluTanTs or excess maTerials have been TransporTeD offsiTe To cenTralizeD sysTems for sTorage (lanDfill), or processing (sewage TreaTmenT planTs). wiTh rising energy cosTs anD sTricTer Dumping or Discharging proTocols, This paraDigm has begun To shifT To in-siTu sTraTegies.

surrounding buildings through a combination of filter substrate and water plants. Various substrates and materials are currently being studied for their capacity to biodegrade excess nutrients or harmful compounds in wetlands, biotopes, and bioswales.

The restoration of the Besòs River addresses a different site context and digestive configuration. Subsurface wetlands are embedded in a riverbed to intercept and treat sewage effluent below the ground surface using plants and bacteria to take up excess nutrients or biodegrade chemicals. The digested water then becomes the river’s source of flow during dry weather. In contrast, the BioHaven™ Floating Islands introduce a mobile Digestive system deployed within water bodies. As with stationary wetland structures, mobile islands foster the natural uptake of pollutants and establish their own habitat and food chain.

Airborne chemicals also require methods to intercept and biodegrade the migration of pollutants. Photocatalytic cement traps and then decomposes airborne pollutants into innocuous elements; Naturaire® vertical plantscape is designed to take up or break down interior airborne pollutants.

Soil-based resources may combine the two scales of Digestive operations by employing both biological remediation via plants, bacteria, or fungus (mycoreme- diation), as well as macro strategies of cut and fill or concealment (capping). For example, the former British Petroleum Park combines three different Digestive operations: onsite soil bio-remediation; the introduction of coastal wetlands to continually cleanse polluted runoff; and the reuse of the site’s infrastructure in order to redirect runoff to the wetlands.

Cultuurpark Westergasfabriek and the Urban Outfitters Navy Yard best exemplify macro-Digestive strategies, reconfiguring site materials to contribute to determining circulation, topography, plantings, and program. The former sets up strategies of polluted soil cut and fill, while the latter reuses the existing inorganic concrete surface to create a porous and vegetated surface.

Digestive // 101 ■